I recently got the go-ahead from my boss at Condesign to open-source ProX, my XML processing XML and its first implementation. It sounds rather more than what it actually is – right now there’s a wrapper pipeline, an XForm, some XSLT and an example DTD – but I happen to think ProX is pretty cool and potentially useful.
I’ll make the stuff available at Github as soon as I have the time, of course with a proud announcement here. In the mean time, you can get an idea about what ProX is by reading my Balisage papers ProX: XML for interfacing with XML for processing XML (and an XForm to go with it) and Using XML to Implement XML.