D&D data for donjon, BECMI and AD&D
The /adnd/ directory should provide a useful example of the directory structure and file format used by the donjon backend. The file format is not JSON, but its structure and syntax is easily discernable if you're familiar with that.
Content taken from the D&D rulebooks should be limited to names, references, and basic statistics where useful. No verbose descriptions of anything. Firstly, they're not used. Secondly, they're impossible to argue under fair use. Pull requests which include significant amounts of copyright material will be rejected.