I see you got the memo that being dismissive of everything that contains buzzwords is still popular ;)
Both IPFS and blockchain are definitely applicable to decentralizing applications. E.g. DSound[0], a distributed version of Soundcloud is built with IPFS + a blockchain(not necessarily a fan of STEEM though). There could just as well be something analogous for Github, Bitbucket, etc..
Blockchains allow for a distributed, mutable permissioned system that are required(?) for features like "Who is allowed to push to this named repository?".
You can also leave stuff like that out, but then you will end up with a system where everyone can only push to their own forks leaving us with a very splintered distributed system. To compensate we would need a much better system for distributed content discovery than anything I've seen so far.
Yeah, I guess you are right, a blockchain is probably not an absolute requirement for that. I think though, that decentralized maintenance of open source project would be a logical next step, and a blockchain-based system could certainly be useful there. This could help prevent a lot of stale/abandoned projects from dying where the only maintainers of a project leave it to rot and there is no one left to review PRs coming from the community.