I just created a merge request,
https://framagit.org/hubzilla/addons/merge_requests/152It is a flashcard software that uses spaced repetition as a learning technique.
Maybe it is of interest for somebody. I find it very useful to learn Italian. You can share your own stuff between different devices and you can share stuff with other learners. If somebody adds or changes the content the other learners will get the changes.
The permission system is simple because he addon uses the cloud storage of hubzilla and its permissions.
A first unpublished version used the DB to store the content.
The current version works a little bit like wikis or webpages. There is an owner of the files. Observers can use the files (flashcards) but they will not own it The files never leave the channel of the owner.
The next planned version should add the ability for an observer to import the flashcards. If you import flashcards from another user you will get a copy and own the copy. The copy "knows" its original and can sync with the original.
I would be pleased if somebody could review the code.