If the primary forge's only job is to host the actual Git infrastructure (the code, the MRs, the issues, maybe a wiki), it's a lot more simple than GitHub, and probably more within the scope of what people can reasonably administer themselves.

I hosted the first "java.apache.org". I was an early employee at CollabNet, and in the first discussions around starting subversion. I worked on Cloud Foundry.

This stuff isn't easy and I'm more than happy letting someone else do it at the expense of some downtime.