I can deliver but not in Java. I have my own SS7 stack including m2pa/m3ua/mtp3/sccp/tcap/gsm-map/sms. MWI is a specially crafted SMS.
Update:
delivery as source in ObjectiveC running under Debian using GnuStep, ulib, ulibasn1, ulibm2pa, ulibmtp3, ulibsccp, ulibtcap (all open source) and the custom application (non open)
App will provide built in http server with a simple API
to be provided: m3ua or m2pa connection for development testing. And specification documents if possible (the traces on the URL you gave me however are very good starting point and could be sufficient to get something working)