That is correct. The backend covers enterprise features that are only source-available, whereas the rest of the application is open source. We understand that this can be quite misleading, and will refrain from saying that we are open source in the future
I also suggest you add documentation to the github repo. The first thing I did after reading the first paragraph of this announcement was checking the source code. And when I saw no documentation at all - zero - nada - niente, I completely lost interest in looking more into the project (I was quite enthusiastic, given your description, so seeing no docs was an incredible turn-off).