Does the Intel Xeon Phi coprocessor, to be usable as parallel platform, require a license of the Intel Composer XE compiler, or are there alternative compilers?
There are a few options I can list here to use/get the Intel compiler...gcc, as you know, is not equipped to vectorize code for this platform.
There is a non-commercial license of the Intel compiler for Linux* that provides the same Intel Xeon Phi coprocessor enabled Intel Development tools as a commercial/eval/academic license assuming the requesting individual fulfills the licensing requirements. http://software.intel.com/en-us/non-commercial-software-development.
For academic institutions who may need licenses in support of a class / training development, a 1-year free license may be obtained. You can find out more at http://software.intel.com/academic > Software Tools ('Request license' button)
A 30-day eval license can be obtained - if you go to the Intel compiler page, there are links to download a 30-day free trial (on the top right corner)