Yes, I’ve come across the Open Question Library but it is just for WeBWorK as you mentioned. The huge issue with WeBWork is that the format is basically a superset of the Perl programming language and this is a show-stopper as an exchange format. Definitively need to come up with a structured format and convert from WeBWorK’s .pg format to this new structured one. Numbas & iMathAS have a much nicer, contained, documented and structured format which could be the basis of this new format.