Building Java SE 6.0 (Mustang) on Windows

Does Sun's use of the Microsoft Visual C++ compiler limit participation in the funfest that is the Mustang Collaboration effort. The Linux and Unix guys have free development tools. The Unix and Linux builds utilize open and free compilers. Not so for Windows. Windows participants must use MS VC++...nothing else will do. That means that if you want to help out in the Mustang effort, you must have Microsoft development tools, and they're neither open nor free.

So this makes me ask these questions:

• Is Sun effectively limiting the participants to Linux and Unix developers by requiring MS tools to build Mustang on Windows?
• Are the majority of community provided fixes going to be platform specific for Linux and Unix?

What do you think?