Is there any point to switch to Forgejo for my open source projects? Wouldnt I just be leeching resources from the guys at Codeberg/ whereever instead of Microsoft?

Codeberg _wants_ to host open source projects; it isn't leeching any more than adding articles to Wikipedia.

If you feel guilty, you can self-host Forgejo, contribute to Forgejo, or become a Codeberg member and pay them a yearly fee of your choosing (https://join.codeberg.org/).