If I could get the same bells and whistles by wiring up another forge, so long as it offered a decent API and/or sent events over a webhook, I'd have everything self-hosted.
The agents would need to expose an interface on their own end but as long as you implemented it with a plugin, it'd take the dependency of GitHub and you could use MCP or skills for the rest of it.
Which is to say, this is perfect for agents given they don't need any bespoke SDK from us: simply write Tangled records for issues, pulls, whatever to your PDS and it'll show up on Tangled. We plan to start working on some exemplar agents first-party that would 1. enhance Tangled itself, 2. showcase cool things you can do with an open data firehose.
The fact that you use a protocol to define it is beside the point. You still have to define what a Tangled record is, and the interface that accepts it, and the mechanism to resolve it on the client.
How else do you define what a 'tangled' is even if the underlying structure is git.