QuickTime is an open standard container for timed multi-media. It is free to implement. The NeXT guys made their own version of QT called NeXTTime, based entirely on the contents of a forty dollar book published by Apple. QuickTime forms the basis for the ISO MPEG4 specification.

What is not free however, are the codecs used by Quicktime (Sorenson Video, Fraunhofer MP3, QDesign Music, Qualcomm PureVoice, Cinepak, etc). This is the major stumbling block for the implementation of QuickTime on other OSes.