There were some people at Microsoft using GPL software. For example, Microsoft's Virtual Server 2005 R2 supported Red Hat Enterprise Linux, according to this bo

There were some people at Microsoft using GPL software. For example, Microsoft's Virtual Server 2005 R2 supported Red Hat Enterprise Linux, according to this book from 2007 : https://books.google.com/books?id=BAtUWStlEUwC&pg=PA41&lpg=PA41&dq=linux+at+Microsoft+2005&source=bl&ots=S9TAbGgNvP&sig=w9T3mrrdsCpdhCted65ho_6VEcg&hl=sv&sa=X&ved=0CGkQ6AEwCWoVChMInOTjweLsxgIVYnxyCh14hQyy#v=onepage&q=linux%20at%20Microsoft%202005&f=false https://books.google.com/books?id=BAtUWStlEUwC&pg=PA41&lpg=P... . And http://www.cnet.com/news/microsoft-embraces-gpl-opens-hyper-v-to-linux-with-linuxic/ http://www.cnet.com/news/microsoft-embraces-gpl-opens-hyper-... from 2009 says "Microsoft embraces GPL, opens Hyper-V to Linux with LinuxIC: Redmond is proving that it can compete with open source on open source's terms by licensing LinuxIC under the GPLv2 license." That said, the concern is indeed real, as http://www.zdnet.com/article/microsoft-admits-its-gpl-violation-will-reissue-windows-7-tool-under-open-source-license/ http://www.zdnet.com/article/microsoft-admits-its-gpl-violat... from 2009 shows ("Microsoft admits its GPL violation; will reissue Windows 7 tool under open-source license").