FreeBSD specific issues
tla requires GNU diff and patch utilities. I had problems on FreeBSD-4.6 running tla changes, and it turned out to be because I was using the BSD patch. Make sure you give the --with-gnu-diff, --with-gnu-diff3, and --with-gnu-patch options to ./configure. GNU patch is in ports, and I built GNU diff directly. It needs GNU make, too, so run gmake, but that is in the basic docs, I believe.
There is a FreeBSD port for tla (and arch) in the devel category of the ports(7) collection. Using this(these) port(s) will avoid any problem building and using it under FreeBSD.
-- Julien Gabel.
It seems that the devel/tla port is more up to date than the devel/arch port (v1.1 vs v1.0p25 on 2004-02-25). So you will probably want to use the devel/tla port.
-- JukkaZitting
The devel/tla port has been updated to 1.2. I don't think there have been any update to arch/larch anyway recently.