Oh okay I looked it up. H.264 is just the MPEG-AVC standard, CoreAVC was popular because it was the fastest decoder around (really Fing Fast). It uses multi-threads so hyperthreading and dual core chips can play high-def video. CoreAVC's complaint was that the open-source project reverse engineered their software, and that was a violation of DMCA. They then apologized, and it will be back soon!