In general, "commercial" compilers (including gcc) translate OpenMP to standard C (or C++, or Fortran) with calls to an OpenMP runtime library
(e.g. libgomp for gcc) which is in turn implemented on top of standard threading libraries. However, they don't actually generate source code as
an intermediate step: the process is more tightly integrated into the overall compilation process, and there's usually no facility to generate a source code representation of the transformed code. The nearest you can get is to dump an intermediate representation which is C-like, but not C, for example with the gcc flag -fdump-tree-optimized. This will contain calls to libgomp, for which the source code is public. However, from a programmer's point of view, this probably isn't especially useful.
Some research compilers, for example OpenUH http://web.cs.uh.edu/~openuh/
, can actually produce the transformed source code.
Hope that helps,