They are mostly open source and promise to become moreso and they have kept their promises so far. They have a standard and their model is flawed but based on a genuinely open, federated protocol. I have some qualms about the privacy afforded by their model but that's neither here nor there in terms of open source strategy.
Is it strategic for us, the open source community, to say "this is good enough" to hop onto this platform and gain access to this growing audience of, frankly, normies?