Currently, the Lemmy Project only uses Github for its repositories related to Lemmy’s development (e.g. Lemmy, Lemmy-UI). GitHub is a proprietary service, and it is owned by Microsoft. These facts open the door for a myriad of potential issues across the ecosystem, and community. I would like to clarify, though, that I don’t think that it would be a wise decision, currently, to remove Github as the primary location for development, but I would think that it would be a good move to mirror Lemmy’s repositories to a FOSS service (e.g. Codeberg). I personally would advocate for the use of Codeberg, as it is entirely open source, and non-profit, and they are currently working on implementing federation (through ActivityPub) – all these things, I think, align well with Lemmy’s role in the wider community, and its more general philosophy. In the future, I would ideally hope for a permanent move to such a service, but, in the meantime, I think it would, at the very least, be a wise, if not only benevolent, move.
I decided to post this here, as I felt that it didn't seem appropriate to post it as an issue in any of the Lemmy repos.
Why not? They allow FOSS, so does it really matter if the hosting service itself is FOSS? Since it uses git, it's quite easy to switch to another service if that ever changes, with the main issue being getting outside contributors to also switch. But starting out on something else would just add barriers to getting those outside contributors in the first place, so it's not like that's a strong argument in favor of starting with something else.
Using GitHub doesn't violate their ethics and philosophy even if GitHub itself does. I see no conflict here.