Quiet, or we'll buy you
Incidentally, if you restrict that relevant market to machines that can run z/OS or machines that can run Mac OS X, then they absolutely do have a monopoly, they do tie their operating systems to their hardware, and maybe they should be compelled to make their software available on alternative platforms. But it is going to take a much larger company than TurboHercules to make that argument, and a lot more money is going to have to be at stake in Europe and relating to European companies and European politicians, before TurboHercules even has a chance of anything but running out of money to fund its lawsuits or being bought out by Big Blue to get it to shut up.
Not that buying someone who is suing you to shut them up - as IBM did in July 2008 when clone mainframe maker Platform Solutions made a fuss - should be legal. But it is not precisely illegal, either. IBM has a long history of buying technology companies to eliminate the competition, as do many, many others.
Having said all of that, it is perfectly understandable to want the Hercules emulator to be available as a true alternative to IBM's mainframe iron running its mainframe software, and a perfect fool as well as a genius could readily see that having such an alternative would be a good thing for mainframe shops.
If Microsoft wanted to really cause some trouble, it would blackbox a version of z/OS that runs on a Windows kernel, slap a DB2 emulation layer on top of SQL Server, put natively compiled z/OS code atop the Hercules emulator inside Hyper-V partitions, and be done with it. That would cost lots of money - but then again, Microsoft has lots. ®