ForgeFed is a federated code collaboration protocol (Think of it as Mastodon and GitLab were combined.)
https://forgefed.peers.community/
Why don’t developers using other, self-hosted platforms? (like Gitea) Because nobody would contribute.
There is no point for a service being open source (I know it’s planned to later publish the code of Nest), if you can’t self host it, because nobody wants to use your hosted instance. There was no point in Gitter being open source, because if you self hosted it, you couldn’t talk to anyone. It was still a walled garden. (They at least realized it, and decided to switch to Matrix as backbone of gitter.im, opening up for the entire Matrix federation.) So you have two choices with a non-federated software forge:

• Run your own server with nobody contributing.
• Use the single hosted instance that everybody is on.

Federation means you run your own server, or if you cant afford, then use one hosted by a volunteer, but you can still contribute on every other server.
There is discussion about implementing ForgeFed in Gitea.

I second that this is good ide a, I personally use gitlab for a lot of things now, but because of ubiquitousness of github it where I find most projects. Amassing more projects like together would really help reduce that issue.

I would keeping it optional is needed too as some orgs may have requirements limiting engagement like that.