See COPYRIGHT file:
Permission to use, copy, and distribute this software and its
documentation for any purpose with or without fee is hereby granted,
provided that the above copyright notice appears with all copies and
that both that copyright notice and this permission notice appear in
Permission to modify the software is granted, but not the right to
distribute the modified code. Modifications are to be distributed as
patches to the released version.
This software is provided "as is" without express or implied warranty.
This license was discussed in Debian here:
They came to the conclusion that it is non-free, because it doesn't grant the right to distribute binaries compiled from modified sources.
(I'm also not sure about the name of the license. dev-libs/mapm itself is no longer distributed under these terms, see bug 452594. So maybe licenses/mapm should be updated to mapm's new terms, and the above be added as licenses/mirror or licenses/tiers?)