MIT/Apache 2.0

[ryo33]

In the Rust community, a dual license under MIT/Apache 2.0 is common, and Rust itself is so.
A typical example is Bevy, which was initially MIT licensed, but they worked hard to relicense it.

The reason why the dual-license is reasonable is discussed in bevyengine/bevy#2373, and it says:

1. The MIT license (arguably) requires binaries to reproduce countless copies of the same license boilerplate for every MIT library in use. MIT-only engines like Godot have complicated license compliance rules as a result
2. The Apache-2.0 license has protections from patent trolls and an explicit contribution licensing clause.
3. The Rust ecosystem is largely Apache-2.0. Being available under that license is good for interoperation and opens the doors to upstreaming Bevy code into other projects (Rust, the async ecosystem, etc).
4. The Apache license is incompatible with GPLv2, but MIT is compatible.

Fortunately for parol, the number of contributors has not exploded yet, so that it will be easy.

[jsinger67]

I already considered a dual license but haven't done it yet.
Now I think it's a good time to do it. I will add Apache 2.0 as an alternative license to parol.

[jsinger67]

Fixed with 0ccc0ba and 59e42b0