Microsoft GPLs Linux virtualisation drivers
Microsoft has announced that it is releasing it's Hyper-V Linux drivers as GPL licensed software. The drivers allow Linux operating systems, running as guests of Microsoft's Hyper-V virtualisation to bypass the emulation of hardware and talk directly to the hypervisor for I/O operations. This in turn improves the performance of the hypervisor and the guest operating systems.
Last year, Microsoft was developing LinuxIC, Linux Integration Components for it's Hyper-V virtualisation, but, as LinuxIC neared release, it was withdrawn from distribution, apparently due to licensing issues. The Linux kernel is licensed under the GNU General Public Licence (GPL) v2 which requires any drivers linking to the kernel also to be licensed under the GPL.
Although some commentators have suggested that this is "Microsoft embracing the GPL", the move is driven more by competition from VMWare and other Linux virtualisation products which can already offer integration support for Linux. That Microsoft released the code as GPL licensed software is more an acknowledgement that the Linux kernel's GPL does make demands of companies wishing to integrate their own code with the kernel and to distribute it.