fighting against an open source monopoly.

It's nearly impossible to write an OS kernel using only portable C, and 
the Intel C compiler actually pretends to *be* GCC and implements a lot of 
GCC extensions in part so that it can compile the kernel.

As for C++ compatibility, I thought the Intel compiler conformed to the 
same (originally Itanium) C++ ABI as GCC, HP C++, and others do: there 
have of course been bugs in this conformance, but that hardly makes a 
monopoly.