Comment by noirscape

Forge federation seems like a bad idea to me. If you want to go the route of decentralized project management (note that git as a VCS tool is already decentralized for this purpose), you're probably much better off modernizing the git-over-email workflow instead.

Decentralizing the code isn't an issue; cloning repo's between servers is so standard that any forge can import a code repo from any other forge.

The difficulty is ancillary stuff like issue trackers, wikis and MRs, but using a federated protocol for that seems ill-advised given the much weaker safeguards against spam. Mailing lists have a very large existing body of work on the matter of dealing with spam and a proven method of mirroring/archival. (Most git wikis are just git repositories with a different renderer.)

The main reason nobody likes doing git-over-email is mostly just because it's very user-unfriendly to set up (since modern mail clients typically aren't correctly configured to deal with them). It's a very developer oriented workflow in the worst way possible. A modernized mailing list program that automatically takes care of things like reformatting emails/not leaking email addresses to the general public would go a long way to make it easier to deal with.