Hey Padarn W. - Phoenix is definitely open to contributions with the caveat that there is a set of core contributors and maintainers that are largely responsible for building out the roadmap functionality (as it is their full-time job). But if there are issues of interest, issues tagged as help wanted or if you file an issue and we label it back for contribution, we'd love your contribution!
We also have a small group of OSS contributors that meet with us twice a month during our community meeting and that's a great way to work more closely on the project as well. Hope that helps.
