In 2006 Microsoft launched its CodePlex open source code hosting site, to provide hosting for open-source developers targeting Microsoft platforms. In July 2009 Microsoft even open sourced some Hyper-V-supporting patches to the Linux kernel, because they were required to do so by the GNU General Public License, and contributed them to the mainline kernel. Note that Hyper-V itself is not open source. Microsoft's F# compiler, created in 2002, has also been released as open source under the Apache license. The F# compiler is a commercial product, as it has been incorporated into Microsoft Visual Studio, which is not open source.