MPEG 4 Technology
MacWorld UK reports that the MPEG-4 Industry Forum completed interoperability testing... which means that MPEG-4 Video encoded with different products will be playable by any decoder:
MPEG-4 offers something that RealNetworks and Microsoft dont: choice. If you want video coding technology from Microsoft, then Microsoft is your vendor. With MPEG-4, theres a choice of multiple vendors
According to the article, the MPEG-4 Industry Forum "is positive that the [licensing] issue will be resolved."