Wikipedia has a full article on this subject at http://en.wikipedia.org/wiki/Dual_license that you should consult.
Some users of the Intel® OpenMP* runtime want or require a COM license, and do not want to build the runtime from source code, while on the other hand providing source code access allows other projects to benefit.
The commercial license for Intel® software can be found at http://software.intel.com/en-us/articles/end-user-license-agreement; when reading that license it is useful to know that the OpenMP* runtime library (libiomp5.so) is listed in the credist.txt and fredist.txt files, so is ‘Redistributable’.
The Intel® OpenMP* runtime source code is available under a BSD-based open source (OSS) license. Please check the license text for authoritative details of its terms.