This didn't belong in the microcontroller FPGA forum so this is the only place I think it fits.
http://www.visualstudio.com/en-us/products/visual-studio-community-vsNote: don't try to open with old versions of windows internet explorer because it won't work right, it works fine with explorer 11 though
Anyway, free as in free to use for free or paid apps.
non-enterprise organizations, up to 5 users.
enterprise organizations (meaning those with >250 PCs or > $1MM in annual revenue), no use is permitted beyond the open source, academic research, and classroom learning environment scenarios.
Windows, Android & iOS.
C++, Python, HTML5, JavaScript, C#, VB, and F#.
Designers, editors, debuggers, profilers.
Web tooling for ASP.NET, Node.js, and JavaScript.
Visual Studio Community 2013 includes all the great functionality of Visual Studio Professional 2013, designed and optimized for individual developers, students, open source contributors, and small teams.
Requires Windows Server 2008 or up, Windows 7 (SP1) or up
Yup you can develop windows phone apps too, not sure about Arm x86 or 64 bit Android Lollipop.