Licensing: Please decide on a license.

[OWL4C]

Hello there! I understand that the crate is still under development, but having a licensed set up already can help with giving potential users security and could help them decide whether to use the crate or not.
Since you are inspired by SymPy, i would suggest looking into Permissive Licenses like the MIT or BSD Licenses, since SymPy apparently uses modified Versions of BSD.