Thanks for wanting to contribute to NICOS.
While we offer a mirror of the code on https://github.com/mlz-ictrl/nicos, our primary repository is our Gerrit Code Review server at https://forge.frm2.tum.de/review/q/status:open+project:frm2/nicos/nicos.
We will discuss and accept pull requests for small changes on GitHub, but for larger-scale changes we ask that you contact us to get access to the Gerrit Code Review system, where it is much easier for us to keep track of such work.
We use a PEP-8 based style. You can find more info in our wiki at https://forge.frm2.tum.de/wiki/projects:nicos:codingstyle