Sven
Release management
This is a philosophical and adoption point here its not always possible to be backwards compatible when you are introducing new features and I would understand if V11 was not backwards compatible with V1.0 which is after all a beta.
The key questions are about long term mainteance costs and TCO if Adapt is to produce courses that are build deployed and used then this is not a problem, but it seems much more capable than that I would encourage you to build in backwards compatability if possible, even if its done with migration scripts.
Clearly if people move from the straight and narrow and introduce their own code then that's their issue. Long term viability of an open source project is all about the non-functional requirements. The bash scripts I wrote 20 years ago still work :)
Adding to JSON
I really like the elegance of holding all the content in json and can see how this will give the project a very long life. I am already thinking about storing each doc as a seperate document in git or on a mongo server and the doing a pull, assemble, build and release.
If you can keep it to json + ,media assets then that gets my vote for what its worth.
I pushed my first adapt course into a Moodle server today - some issues (see latest post) but it went in like a dream.
Best wishes
D