Duck Corp. (now On2) released GPLed source of their solution VPVision (capturing software for Windows), and it contains sources of their two codecs – TrueMotion 1 and TrueMotion 2 (predecessors of VP3-7 family).
TrueMotion 1 decoder is already present in FFmpeg, now it’s time to add TrueMotion 2.
The bad thing is that codec source code is poorly-documented and optimised for performance (optimisation is a form of obfuscation and vice-versa – look at The International Obfuscated C Code Contest for examples).