Nobody says you have to use Apple iTunes because plenty of competitors currently exist. There is no law on the books stating that a company is not allowed to have proprietary software. The problem with proprietary is that the market usually slaps it down so Apple can enjoy the closed Fairplay DRM until such a time as market pressure dictates they need to open it up. They likely can't hold onto 75% market share forever. Then again, Microsoft has for well over a decade.
Microsoft's lawsuits have typically come as a result of shady activity in squashing the competition. But such suits usually fail in areas where it has been shown that Microsoft did nothing illegal.
although microsoft has "unfair bussiness practises". i think some of these companies are just after change from microsoft . i say so because apple co. ties in Quicktime and itunes in thier os and nobody says anything .you can't play itunes DRM music on other mp3 devices . but microsoft is being sued by the EU and other companies (which produce software which is more crappy than the crap we get from microsoft ).
But i have to give a heads up to microsoft for their cool stunt which they did to nullify the U.S gov anti trust suit (combining windows explorer and I.E).These other companies should create their own OS and tie their own crap on it , not try to be a leech on ther peoples success