Numberfields has also published their code:
https://numberfields.asu.edu/NumberFields/forum_thread.php?id=488&postid=3063#3063

There is alredy (on sourceforge).
I'll change the link

I was wondering which BOINC projects are open-source? Thanks

This is a list of open souce projects

In January 2006 we launched an initial release BOINC client which we alpha tested in a small group, but we ran into some significant issues with the client. In April we updated much of the code, but we had to deal with a staff turnover in the BOINC part of the development team, which slowed development. As of June 2006 we are putting this platform on hold, as until such time as our staffing situation changes, and the incompatibilities on both sides are resolved, further development has been shelved.

A list of the projects we're aware of is here.
Folding@Home is pushing a lot of COVID-19 work now if you can get it. Their servers are overwhelmed by all the compute power that's come online in the last few days. That's causing problems both getting and returning work, at least for GPU clients. Work assignment is also buggy, the client can get hung on a server that's not responding or issuing work and won't move on to another. I've set up exclusions in BOINC so that if my machine can't get FAH work, BOINC will resume. If you can put up with these quirks the work has run without any problems for me.