QuickTime is more than a movie player - it is a complete media API. It has an installed base of over 100 million and is a mature, well maintained framework. This means that it has an extremely stable codebase and is widely deployed and tested on a variety of machines. Secondly it provides quality support for different media formats. You will find that many other technologies list a large number of media formats but provide only token support for each of them.
When installing or updating QuickTime you'll need to select a 'full' or 'authoring' install. ImageGlue is designed to work with QuickTime 5.0 or later.
Under some circumstances it may not be possible for you to install QuickTime on the server. ImageGlue will work in the absence of QuickTime but you will not be able to import or export QuickTime movies and other formats.
If you would like more information on QuickTime, the QuickTime Specification is a good starting point.