I don't want to strangle anyone's project in the crib, but it needs post attribution at the very least. I can understand it being a project in the early stages, but it's not hard to include info on the source of the posts.
However, if they had that but weren't yet open source and had only one-way federation, I would be open to giving them a date to hit for those. I don't like the idea of one-way federation, nor of federation with a closed-source project, but to take the dev at face value and allow them a time frame of 6 months or so to clear it up would be acceptable.
All that being said, as it stands now I would vote to defederate due to the lack of attribution. It is the very least that could be done and shouldn't be hard to implement.