OK, IANAL, but I think you’re missing the point of the anti-trust case. They aren’t being sued for being successful, or even for being a monopoly. They’re being sued for abusing their monopoly power, by trying to extend that monopoly into other markets (specifically, the internet browser market) using anticompetitive buisness practices.
It works like this. I have a monopoly on oil refineries, you make natural gas powered car. Its not legal for me to start giving gasoline powered cars away for free to drive you out of buisness.
Thats essentially what MS was trying to do, not by giving away IE for free (NS was also free), but by controlling access to it. PC manufacturers weren’t allowed to modify the desktop icons - which included IE - or the startup screen - which said something like “Windows 98 with Internet Explorer”.
Now, you could argue that, what with MacOS, BeOS, and Linux, MS never had a monopoly in the first place. Jacksons unusual definition of the market that MS had a monopoly in is probably going to be argued in the appeal.
Important to note is that the quality of the browsers didn’t matter. I personally think that since version 4, IE has been much better than NS, and I, as a programmer, have benefitted from having IE integrated with the operating system. Nor does the MSs track record on innovation, which is very arguable, or their bringing computers to the masses.
Oh, and theres also the Sun and Intel things, but those have sort of passed by the wayside.
Check out this link for more detail on the case. Its got some of the best coverage I’ve seen.