Mark this day in your diary: Microsoft has decided to use the GPL for some of its software.
This is according to Matt Asay over on our American sister site CNet News, who reports that the Hyper-V Linux Integration Components, which are low-level software components that integrate tightly with the Linux kernel to make it work better with Hyper-V, are being released under GPL 2.0. GPL 2 has the relevant bits for kernel integration - and also avoids the hard-core patent defence clauses in GPL 3, which may be more than Microsoft can swallow just at the moment. The company is still dedicated to making companies buy licensing for its FAT patents, after all.
Pal DJ, who runs the annoyingly good H-Online site, also points out that the Linux components were available last year in RC2, but got pulled due to licensing considerations. It's presumably taken Microsoft the intervening year -- and, one imagines, some very interesting internal meetings -- to bite the bullet and do what has to be done.
Hyper-V's lack of Linux support has been hurting it in comparison to its non-Microsoft competition, none of whom have any compunction in supporting the sort of heterogenous environments which commonly adopt virtualisation. And you can't go creating kernel-level Linux code that doesn't use the GPL (at least I don't know how and it's a fair guess that Microsoft doesn't, either) - so this could be a very unusual one-off, rather than a wholesale adoption.
But it should at least put paid to any resumption of Microsoft's more intemperate attacks on the GPL - which will also reflect well on the company.