Our community supports open source code and tools for creating and using UEFI firmware.  Our firmware build system is cross platform (Linux, OS X, Windows) and supports various toolchain types (GCC, ICC, Visual Studio, XCode, CLANG).

We have several sample platforms that run under an OS which will make it quick and easy to build and test your project.  (Including user-process based UEFI emulation environments and UEFI virtual machine firmware.)