I stopped using AAAPackageDev myself, I never used most of its features, or they didn't always work how I wanted them to. People have always been requesting the ability to go from tmLanguage to JSON or from JSON to tmLanguage. A couple of days a ago someone asked the same question about converting color schemes.
I created a simple pluign that allows you to toggle between any PLIST to JSON and vice versa. It is here github.com/facelessuser/PlistJsonConverter.
You can just use the Plist Json Converter: JSON to PLIST command from the command palette. It will convert you to a plist, and then you can save the filename as whatever you want. Hopefully that helps.
If you want specific help in getting the AAAPackageDev feature to work, maybe someone who uses will come along with some help.