Since we are electing to use JSON the schema will not automatically be validated; however, MolSSI will sponsor software to validate the schema in a variety of languages. Likely through these implementations.
Yes, we are currently discussing which fields are reserved and where the best place for arbitrary fields would be.
JSON is agnostic to the underlying programming language and is well supported in a variety of languages (C++/Python/JS/etc). We will provide examples on how to write JSON in other languages where JSON is not as well supported (Fortran).
The ability to hand write and tweak a given input has been a sought after property. In addition, the overall structure of JSON is viewed as simpler and more intuitive than XML. As the schema is fully specified it should be possible for the validator to take in a JSON input and return an XML output.
We will support zero-indexing and camelCase in the JavaScript notation. Discussion is underway if we will follow the full Google JSON Style Guide.
Yes, the schema will have version flags so that it can evolve over time.