>>thomas+(OP)
I'm happy to see others in the space, but I wish Anki competitors would implement a decent 'import from Anki' feature. Otherwise, I think most existing users of SRS are unlikely to switch (because we use Anki and have thousands of cards there already).
The data format of Anki is a bit complicated but at least it's SQLite. I've seen a ton of shared decks and resources on ankiweb, but it's true you can't easily put them on GitHub.