This is FBBI, the Flaming Bovine Befunge-98 Intepreter — the "first and worst" of the Funge-98 interpreters available.
It's actually not so bad anymore, after a patch-applying and bug-killing session back in 2011. Still, it should probably not be your first choice for a Befunge-98 interpreter, nor does it claim to be the reference implementation of the language. It was just an early one.
See the file doc/fbbi.md for FBBI's documentation.
FBBI is open-source software, distributed under a BSD-style license. See the file LICENSE for more information.