Contributions are welcome, and greatly appreciated! Every little bit helps, and credit will always be given.
However, due to the incricate nature of open source licensing, any contribution to the PR2 code (not FastDownward) will be assumed to come with the full rights for the PR2 maintainer (Christian Muise) to relicense the code under a different license, if necessary. This is to ensure that the PR2 code can be used in a variety of contexts, including commercial ones. Contributors do not forfeit copyright, but they do grant the perpetual right to relicense the code.
If you need support, want to report/fix a bug, ask for/implement features, you can check the Issues page or submit a Pull request.