Some software packages have restrictive licenses or are in violation to the law (PKP's patent on public key crypto, ITAR (export of crypto software) to name just two of them). What we can do with them vary a lot, depending on the exact wordings of the respective licenses.
Note that it is your responsibility as a porter to read the
licensing terms of the software and make sure that the FreeBSD
project won't held accountable of violating them by
redistributing the source or compiled binaries either via ftp
or CD-ROM. If in doubt, please contact
ports@freebsd.org.
We usually get around this problem by setting
${NO_PACKAGE} in the Makefile, and not putting
the distfile up for ftp. However, for most cases, you should
at least be able to make a port, so don't let the license
scare you away!
Note: The GNU General Public License (GPL), both version 1 and 2, shouldn't be a problem for ports.
Note: If you are a committer, make sure you update the
ports/LEGAL file too.