I've got PEG.js parsing all the GIFT examples I could find. Have a look at the online development environment:
The GitHub repository has automated tests (using node.js and mocha). I've not used the JavaScript objects for anything real, so perhaps there are better ways to format them. The hard part is the parsing, and I think it's mostly done. Hope this is useful to someone.
My next goal would be to write some kind of auto-completion editor for GIFT questions, to make them easier to write. Let me know if you're interested in working on this.