LEOPOLDBLOOM It's not really clear what you're asking. Like the developer said, Perian's Type Installer doesn't add any functionality to QT. But, if you're using QT (including Pro), Perian _does_ add functionality. QT Pro has many more options for converting, exporting, etc. than the regular version, but it still suffers from the same codec limitations. Perian solves this for you by adding a large variety of codecs to QT's library, making it a VLC-like media player that will handle just about any file format or codec you throw at it.
Perian's type installer simply allows your computer to recognize file types that QT doesn't support by default as QT files. For example, if you have an MKV file and it's set to open with QT (which will play it with Perian installed), it will still be described as a UNIX Executable file in the Finder because it's not a supported format by default. Perian's Type Installer causes files like this to be properly recognized and labelled as QT files.
(Version 2.4.3_TigerFixed)