I haven't seen this mentioned in the thread but it seems relevant. The Reliable Data Protocol (RFC's 908/1151) is built on UDP and can deliver reliable, out of order data packets without bringing in congestion control and other features of TCP. It looks like there's a pretty complete Java implementation of it developed as part of a larger project by USC.
A link to an explanatory article on their use of RDP and the implementation they provide:
The project homepage: