it is common for the source to include third-party libraries that have per-seat licenses.
but for the compiler to mandate a library that has such a license?
or for a compiler to require per-seat licensing of the binaries that it produces???
even in the cases of proprietary compilers, you could make your source code link against a free library and not worry that using a particular compiler 'tainted' the resulting binary so that you couldn't use it without the approval of the compiler company.