Bitgen 0.12 has been released:

http://bitcoin-gen.org/

The release includes Windows support in addition to refactoring changes and improvements to the software tests.

No Windows binary is included (yet) since it is easy to build for Windows,
and to encourage building from source.

It is possible to build for Windows both on Linux and Windows, using Linux is actually easier than Windows.

On Linux the mingw-w64 cross compiler is used for the build.
On Windows MSYS2 is used.