Ballmer is a d.h.
Open Source software is almost invariably developed initially on some sort of unix -- whether that be GNU/Linux, one of the BSDs or Solaris -- and only gets ported to Windows because there was no good reason not to. I'd love to be proven wrong, but I cannot honestly think of a single example of a piece of software which was originally developed on Windows and later ported to unix. Also, the fact that TrollTech's Qt libraries have long been available under the GPL (and therefore TrollTech could not prevent anyone from porting them to Windows) yet nobody actually *did* port them, serves only to reinforce my thinking that most developers on the Windows platform are more interested in pirating closed-source payware and developing malware than in developing Free Software.
As for Ballmer's speech: European and British law specifically *excludes* software from the scope of patentability, so GNU/Linux -- being pure software -- most certainly is *not* infringing any valid patents in the UK or on the Continent. European and British law also specifically exclude enforcement of a new law after the fact; so if British or European law ever changes such that software becomes patentable, then everybody will have to apply for brand new patents (which most probably will be refused on the grounds of prior art).
And does misrepresenting the law and falsely accuses people of illegal acts [though in this case, the falseness of the accusation derives not from the alleged perpetrators not committing the acts, but from the non-illegality of the acts] with clear intent to scare potential Open Source customers into using Microsoft software and thereby securing financial gain for Microsoft, constitute fraudulent advertising?