gnusocial
Check the programme page to learn more about the programme and on how to apply.
GNU social is a social communication software used in federated social networks. It is widely supported and has a large userbase.
If you would like to know how is it like to be a GSoC student at GNU social, read this blog post!
Usually we participate in Google Summer of Code and are thus are able to give accepted students a stipend. It's not the case this year. Last year we've had a successful student supported by The Freaks Club, you can reach thndrbvr and try your luck, or look for another sponsor.
The community has not proposed ideas for 2021 yet. As the current development team is planning on major active development of v3 with NLnet sponsorship this year, as a student you can either try to join the development of v3 or contribute with plugins for v2, which is the latest release.