I mean, that’s not surprising though is it? If a FOSS tool I made has an additional feature that requires my own backend to support, then there has to be a backend to support it.
The FE that uses it is still FOSS, and one could always build their own API to the specs outlined by the client.
They could OSS their server side code ofc, that’d be cool. But that also takes sometimes double the effort to do well, and keep custom tweaks and changes either separate and proprietary, or build out a complex way for them to be dynamically injected. So I don’t really blame them on that one tbh.