How important is Posix?
hapless: Windows has had a first party UNIX solution for a very long time: Microsoft SFU/SUA.  It's bundled with Windows 2003R2.  On all earlier versions, you have to go download SFU 3.5 separately.http://technet.microsoft.com/en-us/library/cc779522.aspxIt incurs no additional license cost. It's POSIX conformant. It comes with both GCC and an MSVC wrapper for use with traditional UNIX build tools.In my experience, it's considerably faster than cygwin, but software compatibility isn't as good.