http://permalink.gmane.org/gmane.os.freebsd.devel.infiniband/30
Sven,
I saw an entry in the mailing list (above link) from a Mellanox employee who's the OFED-FreeBSD Team Leader. It looks like they are writing the drivers but are submitting them as open source. The userland tools appear to be identical to the Linux tools.
The tools need to be built from source but it's fairly simple...
cd /usr/src/contrib/ofed && make includes
cd /usr/src/contrib/ofed/usr.lib && make depend all install
cd /usr/src/contrib/ofed/udr.bin && make depend all install