diff --git a/pyproject.toml b/pyproject.toml
index c0c6ea067..7efd03090 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,13 +34,11 @@ classifiers = [
 dynamic = ["version"]
 dependencies = [
     "resdata",
-    "res2df",
     "ert>=10.2.0b13",
     "fmu-tools",
     "grid3d_maps",
     "matplotlib",
     "numpy",
-    "opm>=2023.04",
     "pandas",
     "pydantic",
     "pyscal",
@@ -55,6 +53,9 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
+res2df = ["res2df"]
+opm = ["opm"]
+all = [res2f, opm]
 tests = [
     "mypy",
     "pytest",
diff --git a/src/subscript/__init__.py b/src/subscript/__init__.py
index c8ee202ae..71fbe711d 100644
--- a/src/subscript/__init__.py
+++ b/src/subscript/__init__.py
@@ -1,6 +1,5 @@
 import logging
 import sys
-from pathlib import Path
 
 try:
     from importlib import metadata
@@ -10,21 +9,6 @@
     pass
 
 
-def detect_os(release_file: Path = Path("/etc/redhat-release")) -> str:
-    """Detect operating system string in runtime, just use default if not found."""
-    default_os_version = "x86_64_RH_7"
-
-    if release_file.is_file():
-        with open(release_file, encoding="utf-8") as buffer:
-            tokens = buffer.read().split()
-            for t in tokens:
-                if "." in t:
-                    major = t.split(".")[0]
-                    return f"x86_64_RH_{major}"
-        raise ValueError("Could not detect RHEL version")
-    return default_os_version
-
-
 def getLogger(module_name="subscript"):
     """Provides a unified logger for subscript scripts.
 
diff --git a/src/subscript/check_swatinit/check_swatinit.py b/src/subscript/check_swatinit/check_swatinit.py
index ce5e7797c..7faee3085 100644
--- a/src/subscript/check_swatinit/check_swatinit.py
+++ b/src/subscript/check_swatinit/check_swatinit.py
@@ -8,7 +8,13 @@
 import numpy as np
 import numpy.typing as npt
 import pandas as pd
-import res2df
+
+try:
+    import res2df
+
+    _HAS_RES2DF = True
+except ImportError:
+    _HAS_RES2DF = False
 
 import subscript
 from subscript.check_swatinit import plotter
@@ -42,6 +48,10 @@ def main() -> None:
 
     Acts on command line arguments, loads data, performs qc and dumps to
     CSV if requested."""
+    if not _HAS_RES2DF:
+        sys.exit(
+            "Error 'res2df' is required for 'check_swatinit' to work.\n Please install using 'pip install subscript[res2df]' or similar."
+        )
     parser = get_parser()
     args = parser.parse_args()
 
diff --git a/src/subscript/fmu_copy_revision/fmu_copy_revision.py b/src/subscript/fmu_copy_revision/fmu_copy_revision.py
index ec97f560c..52a81f67f 100755
--- a/src/subscript/fmu_copy_revision/fmu_copy_revision.py
+++ b/src/subscript/fmu_copy_revision/fmu_copy_revision.py
@@ -15,9 +15,9 @@
 from os.path import join
 from pathlib import Path
 
-import subscript
+from subscript import getLogger, __version__
 
-logger = subscript.getLogger(__name__)
+logger = getLogger(__name__)
 
 DESCRIPTION = """This is a simple interactive script for copying a FMU revision folder
 with features:
@@ -293,7 +293,7 @@ def get_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--version",
         action="version",
-        version="%(prog)s (subscript version " + subscript.__version__ + ")",
+        version="%(prog)s (subscript version " + __version__ + ")",
     )
 
     logger.info("Parsing commandline")
diff --git a/src/subscript/fmuobs/fmuobs.py b/src/subscript/fmuobs/fmuobs.py
index d77db4b81..35dbd6976 100644
--- a/src/subscript/fmuobs/fmuobs.py
+++ b/src/subscript/fmuobs/fmuobs.py
@@ -13,13 +13,13 @@
 import yaml
 
 from subscript import __version__, getLogger
-from subscript.fmuobs.parsers import (
+from .parsers import (
     compute_date_from_days,
     ertobs2df,
     obsdict2df,
     resinsight_df2df,
 )
-from subscript.fmuobs.writers import (
+from .writers import (
     CLASS_SHORTNAME,
     df2ertobs,
     df2obsdict,
diff --git a/src/subscript/fmuobs/parsers.py b/src/subscript/fmuobs/parsers.py
index fc5460bb5..8c2c4b591 100644
--- a/src/subscript/fmuobs/parsers.py
+++ b/src/subscript/fmuobs/parsers.py
@@ -9,7 +9,7 @@
 import pandas as pd
 
 from subscript import getLogger
-from subscript.fmuobs.util import (
+from .util import (
     ERT_ALT_DATE_FORMAT,
     ERT_DATE_FORMAT,
     ERT_ISO_DATE_FORMAT,
diff --git a/src/subscript/fmuobs/writers.py b/src/subscript/fmuobs/writers.py
index 39bc15ccb..59d0bff25 100644
--- a/src/subscript/fmuobs/writers.py
+++ b/src/subscript/fmuobs/writers.py
@@ -9,7 +9,7 @@
 import pandas as pd
 
 from subscript import getLogger
-from subscript.fmuobs.util import (
+from .util import (
     CLASS_SHORTNAME,
     ERT_ISO_DATE_FORMAT,
     lowercase_dictkeys,
diff --git a/src/subscript/grav_subs_maps/grav_subs_maps.py b/src/subscript/grav_subs_maps/grav_subs_maps.py
index c93182cac..78c3bf3a5 100644
--- a/src/subscript/grav_subs_maps/grav_subs_maps.py
+++ b/src/subscript/grav_subs_maps/grav_subs_maps.py
@@ -14,9 +14,9 @@
 from resdata.grid import Grid
 from resdata.resfile import ResdataFile
 
-import subscript
+from subscript import getLogger, __version__
 
-logger = subscript.getLogger(__name__)
+logger = getLogger(__name__)
 
 # Constant for subsidence modelling, not influencing results
 # since subsidence is calculated from porevolume change
@@ -111,7 +111,7 @@ def get_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--version",
         action="version",
-        version="%(prog)s (subscript version " + subscript.__version__ + ")",
+        version="%(prog)s (subscript version " + __version__ + ")",
     )
     return parser
 
diff --git a/src/subscript/grav_subs_points/grav_subs_points.py b/src/subscript/grav_subs_points/grav_subs_points.py
index d2784a6dd..f27f6f56d 100644
--- a/src/subscript/grav_subs_points/grav_subs_points.py
+++ b/src/subscript/grav_subs_points/grav_subs_points.py
@@ -14,9 +14,9 @@
 from resdata.grid import Grid
 from resdata.resfile import ResdataFile
 
-import subscript
+from subscript import getLogger, __version__
 
-logger = subscript.getLogger(__name__)
+logger = getLogger(__name__)
 
 # Constant for subsidence modelling, not influencing results
 # since subsidence is calculated from porevolume change RPORV
@@ -133,7 +133,7 @@ def get_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--version",
         action="version",
-        version="%(prog)s (subscript version " + subscript.__version__ + ")",
+        version="%(prog)s (subscript version " + __version__ + ")",
     )
     return parser
 
diff --git a/src/subscript/interp_relperm/interp_relperm.py b/src/subscript/interp_relperm/interp_relperm.py
index fea7bd7eb..b68c9c5e7 100755
--- a/src/subscript/interp_relperm/interp_relperm.py
+++ b/src/subscript/interp_relperm/interp_relperm.py
@@ -11,11 +11,17 @@
 import pyscal
 import yaml
 from pydantic import BaseModel, Field, FilePath, model_validator
-from res2df import satfunc
 
-import subscript
+try:
+    from res2df import satfunc
 
-logger = subscript.getLogger(__name__)
+    _HAS_RES2DF = True
+except ImportError:
+    _HAS_RES2DF = False
+
+from subscript import getLogger, __version__
+
+logger = getLogger(__name__)
 
 DESCRIPTION = """Interpolation script for relperm tables.
 
@@ -288,13 +294,17 @@ def get_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--version",
         action="version",
-        version="%(prog)s (subscript version " + subscript.__version__ + ")",
+        version="%(prog)s (subscript version " + __version__ + ")",
     )
     return parser
 
 
 def main() -> None:
     """Invocated from the command line, parsing command line arguments"""
+    if not _HAS_RES2DF:
+        sys.exit(
+            "Error 'res2df' is required for 'interp_relperm' to work.\n Please install using 'pip install subscript[res2df]' or similar."
+        )
     parser = get_parser()
     args = parser.parse_args()
 
diff --git a/src/subscript/merge_rft_ertobs/merge_rft_ertobs.py b/src/subscript/merge_rft_ertobs/merge_rft_ertobs.py
index 08a2092c6..2e9cb3c6d 100644
--- a/src/subscript/merge_rft_ertobs/merge_rft_ertobs.py
+++ b/src/subscript/merge_rft_ertobs/merge_rft_ertobs.py
@@ -6,9 +6,9 @@
 import numpy as np
 import pandas as pd
 
-import subscript
+from subscript import getLogger, __version__
 
-logger = subscript.getLogger(__name__)
+logger = getLogger(__name__)
 
 DESCRIPTION = """Collect ERT RFT observations and merge with CSV output
 from GENDATA_RFT. Dump to CSV file for visualization in Webviz.
@@ -64,7 +64,7 @@ def get_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--version",
         action="version",
-        version="%(prog)s (subscript version " + subscript.__version__ + ")",
+        version="%(prog)s (subscript version " + __version__ + ")",
     )
     return parser
 
diff --git a/src/subscript/presentvalue/presentvalue.py b/src/subscript/presentvalue/presentvalue.py
index 5e71d6337..c268603fa 100755
--- a/src/subscript/presentvalue/presentvalue.py
+++ b/src/subscript/presentvalue/presentvalue.py
@@ -4,10 +4,16 @@
 import datetime
 import logging
 from pathlib import Path
-
+import sys
 import numpy as np
 import pandas as pd
-import res2df
+
+try:
+    import res2df
+
+    _HAS_RES2DF = True
+except ImportError:
+    _HAS_RES2DF = False
 import scipy.optimize
 
 from subscript import __version__, getLogger
@@ -124,6 +130,10 @@ def main() -> None:
     """Function for command line invocation.
 
     Parses command line arguments, and writes output to file and/or terminal."""
+    if not _HAS_RES2DF:
+        sys.exit(
+            "Error 'res2df' is required for 'presentvalue' to work.\n Please install using 'pip install subscript[res2df]' or similar."
+        )
     parser = get_parser()
     args = parser.parse_args()
 
diff --git a/src/subscript/prtvol2csv/prtvol2csv.py b/src/subscript/prtvol2csv/prtvol2csv.py
index b69426d34..dc501b2b6 100644
--- a/src/subscript/prtvol2csv/prtvol2csv.py
+++ b/src/subscript/prtvol2csv/prtvol2csv.py
@@ -7,9 +7,15 @@
 import warnings
 from datetime import datetime
 from pathlib import Path
-
+import sys
 import pandas as pd
-import res2df
+
+try:
+    import res2df
+
+    _HAS_RES2DF = True
+except ImportError:
+    _HAS_RES2DF = False
 from fmu.tools.fipmapper.fipmapper import FipMapper
 
 from subscript import __version__, getLogger
@@ -327,6 +333,10 @@ def reservoir_volumes_from_prt(prt_file: str, fipname: str = "FIPNUM") -> pd.Dat
 
 def main() -> None:
     """Function for command line invocation"""
+    if not _HAS_RES2DF:
+        sys.exit(
+            "Error 'res2df' is required for 'prtvol2csv' to work.\n Please install using 'pip install subscript[res2df]' or similar."
+        )
     args = get_parser().parse_args()
 
     tablesdir = prep_output_dir(args.dir)
diff --git a/src/subscript/rmsecl_volumetrics/rmsecl_volumetrics.py b/src/subscript/rmsecl_volumetrics/rmsecl_volumetrics.py
index ac9e14495..aa629b043 100644
--- a/src/subscript/rmsecl_volumetrics/rmsecl_volumetrics.py
+++ b/src/subscript/rmsecl_volumetrics/rmsecl_volumetrics.py
@@ -5,14 +5,14 @@
 import logging
 from pathlib import Path
 from typing import Any, cast
-
+import sys
 import pandas as pd
 import yaml
 from fmu.tools.fipmapper import fipmapper
 from fmu.tools.rms import volumetrics
 
 from subscript import getLogger
-from subscript.prtvol2csv.prtvol2csv import currently_in_place_from_prt
+from subscript.prtvol2csv.prtvol2csv import currently_in_place_from_prt, _HAS_RES2DF
 
 logger = getLogger(__name__)
 logger.setLevel(logging.INFO)
@@ -143,6 +143,10 @@ def _disjoint_sets_to_dict(
 
 def main() -> None:
     """Parse command line arguments and run"""
+    if not _HAS_RES2DF:
+        sys.exit(
+            "Error 'res2df' is required for 'rmsecl_volumetrics' to work.\n Please install using 'pip install subscript[res2df]' or similar."
+        )
     args = get_parser().parse_args()
 
     if args.PRTFILE.endswith("csv"):
diff --git a/src/subscript/sector2fluxnum/completions.py b/src/subscript/sector2fluxnum/completions.py
index f6cb8823c..4359f7f1c 100644
--- a/src/subscript/sector2fluxnum/completions.py
+++ b/src/subscript/sector2fluxnum/completions.py
@@ -1,4 +1,8 @@
-from res2df import ResdataFiles, compdat
+try:
+    from res2df import ResdataFiles, compdat
+    _HAS_RES2DF = True
+except ImportError:
+    _HAS_RES2DF=False
 
 
 def get_completion_list(ecl_data_file_name):
diff --git a/src/subscript/sector2fluxnum/sector2fluxnum.py b/src/subscript/sector2fluxnum/sector2fluxnum.py
index 82e834fe5..f3938f0ac 100755
--- a/src/subscript/sector2fluxnum/sector2fluxnum.py
+++ b/src/subscript/sector2fluxnum/sector2fluxnum.py
@@ -5,8 +5,8 @@
 import cwrap
 from resdata.grid import Grid
 from resdata.resfile import FortIO, ResdataFile
-
-from subscript.sector2fluxnum import completions, datafile_obj, flux_obj, fluxfile_obj
+import sys
+from . import completions, datafile_obj, flux_obj, fluxfile_obj
 
 DESCRIPTION = """
 The script sector2fluxnum will execute different steps in a workflow
@@ -225,6 +225,10 @@ def main():
     """
     main method
     """
+    if not completions._HAS_RES2DF:
+        sys.exit(
+            "Error 'res2df' is required for 'sector2fluxnum' to work.\n Please install using 'pip install subscript[res2df]' or similar."
+        )
     parser = get_parser()
     input_args = parser.parse_args()
 
diff --git a/src/subscript/summaryplot/summaryplot.py b/src/subscript/summaryplot/summaryplot.py
index 8de4d852f..971f9eb45 100644
--- a/src/subscript/summaryplot/summaryplot.py
+++ b/src/subscript/summaryplot/summaryplot.py
@@ -34,13 +34,13 @@
 
 # Get rid of FutureWarning from pandas/plotting.py
 from pandas.plotting import register_matplotlib_converters
-from resdata.grid import Grid  # type: ignore
-from resdata.resfile import ResdataFile  # type: ignore
-from resdata.summary import Summary  # type: ignore
+from resdata.grid import Grid
+from resdata.resfile import ResdataFile
+from resdata.summary import Summary
 
-import subscript
+from subscript import getLogger, __version__
 
-logger = subscript.getLogger(__name__)
+logger = getLogger(__name__)
 
 register_matplotlib_converters()
 
@@ -120,7 +120,7 @@ def get_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--version",
         action="version",
-        version="%(prog)s (subscript version " + subscript.__version__ + ")",
+        version="%(prog)s (subscript version " + __version__ + ")",
     )
     return parser
 
diff --git a/src/subscript/sunsch/sunsch.py b/src/subscript/sunsch/sunsch.py
index 2ef4d293f..3c911daf0 100755
--- a/src/subscript/sunsch/sunsch.py
+++ b/src/subscript/sunsch/sunsch.py
@@ -17,9 +17,9 @@
 import dateutil.parser
 import yaml
 from pydantic import BaseModel, FilePath
-
+import sys
 from subscript import __version__, getLogger
-from subscript.sunsch.time_vector import TimeVector
+from .time_vector import TimeVector, _HAS_OPM
 
 logger = getLogger(__name__)
 
@@ -539,6 +539,10 @@ def get_parser() -> argparse.ArgumentParser:
 
 def main() -> None:
     """Entry point from command line"""
+    if not _HAS_OPM:
+        sys.exit(
+            "Error 'opm' is required for 'sunsch' to work.\nPlease install using 'pip install subscript[opm]' or similar."
+        )
     parser = get_parser()
     args = parser.parse_args()
 
diff --git a/src/subscript/sunsch/time_vector.py b/src/subscript/sunsch/time_vector.py
index b4752c47e..5f693e68e 100644
--- a/src/subscript/sunsch/time_vector.py
+++ b/src/subscript/sunsch/time_vector.py
@@ -4,10 +4,13 @@
 from io import StringIO
 from operator import attrgetter
 
-import opm.io
-from opm.io.parser import ParseContext, Parser
-
-error_actions = [("PARSE_INVALID_KEYWORD_COMBINATION", opm.io.action.ignore)]
+try:
+    import opm.io
+    from opm.io.parser import ParseContext, Parser
+    _HAS_OPM=True
+    error_actions = [("PARSE_INVALID_KEYWORD_COMBINATION", opm.io.action.ignore)]
+except ImportError:
+    _HAS_OPM=False
 
 # This is from the TimeMap.cpp implementation in opm
 ecl_month = {