When Logic 9 was released, many users complained that the suite was not officially reported to be working on G5-based computers. However, when looking at the "Read Me" file, one can see the following information:
Of course, the software can be installed and launched on G5-based hardware, however performance will not be optimized and today's CPU are faster than the latest best G5. Some users suspect that Apple acted this way to boost sales of its desktop models, while other, including us, think that Apple does not want to officially support this software on G5 hardware while Snow Leopard (Intel CPU only Mac OS X) is around the corner.