Can confirm that the code compiles and runs appropriately on my raspberry pi 1

mkdir gibmat
cd gibmat/
git clone https://github.com/gibmat/PiCW.git
cd PiCW/
sudo make install

Outputs

g++ -D_GLIBCXX_DEBUG -std=c++11 -Wall -Werror -Wno-psabi -lm -latomic -DRPI1 -pthread mailbox.o PiCW.cpp -o PiCW
install -m 0755 PiCW /usr/local/bin

Verification shows

pi@raspberrypi:~ $ ls /usr/local/bin/
PiCW

Execution shows

pi@raspberrypi:~ $ sudo PiCW --freq 10.140e6 --ditdit --wpm 60
Detected Raspberry Pi version 1
PiCW parsed command line options:
  TX frequency: 10.140000 MHz
  WPM: 60
  NTP will be used to periodically calibrate the transmission frequency
Will transmit an endless series of dits. CTRL-C to exit.

Linux version

pi@raspberrypi:~/gibmat/PiCW $ cat /etc/os-release
PRETTY_NAME="Raspbian GNU/Linux 10 (buster)"
NAME="Raspbian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"

Note: I thought that the use of sudo ./PiCW --freq 10.140e6 --ditdit --wpm 60 in the examples (README) to be confusing.
That code will run only if the user is in the same directory as the executable, else, it will return a very sad sudo: ./PiCW: command not found. The example, in my opinion, should either specify that the example is run from the same directory or, should be amended to sudo PiCW --freq 10.140e6 --ditdit --wpm 60.

Disclaimer: I am a fully licensed Amateur Radio Operator (M0ISI) the trasmission was performed in a LPF on a 20W dummy load and I used a FT-817ND to verify reception (placed beside the Pi).

Does not work.

pi@raspberrypi:~/PiCW $ sudo ./PiCW --freq 10.140e6 --test-tone
Detected Raspberry Pi version 1
PiCW parsed command line options:
TX frequency: 10.140000 MHz
NTP will be used to periodically calibrate the transmission frequency
Will transmit continuous tone on requested frequency. CTRL-C to exit.
Unable to open / create kernel mbox device file, abort!

Unfortunately it looks like @JamesP6000 hasn't actively done anything with this repo in several years now. And looking at the 12 forks, @IsaevTA it looks like you're the only one who has done anything in the past year.

This PR was to get the code compiling on the current Debian release; hopefully within a few months we'll have "bullseye" released, which may yet again need compiler updates. However, at this point in time I consider this a dead project, and as I'm not a CW person, I don't have any personal motivation to try to keep the code working.