From Jacobson Lab Wiki
 Getting Plop
 Academic Use
The executable is available free of charge for academic purposes.
Plop developers can check out plop from a CVS repository.
cvs -d username@hostname:/path/to/cvs/root checkout plop
 Commercial Use
Licensing information is available here.
It is also possible to link against the Intel MKL, however this is not freely available and there may be licensing issues.
After the necessary libraries are installed it may be necessary to update your LD_LIBRARY_PATH environment variable (or update your Makefile to include a -L/path/to/lib) if you have installed these libraries in non-standard locations.
It is possible to compile without ./make_plop.pl, i.e using 'make plop'. To do so, the following environment variables must be set:
$COMPILER = One of the compilers listed from the usage statement of ./make_plop.pl
$PLOP_COMPILER_FLAGS = These flags are passed directly to the compiler
$PLOP_LINKER_FLAGS = These flags are passed directly to the linker
If you inspect the Makefile, you will see these last two environment variables are appended to what is defined for each compiler.
To view an example set of these environment variables run: ./make_plop.pl <some_compiler> dryrun
See: Running plop