Reference/library implementation of OpenFormula?

Does anyone know of any open-source libraries or reference implementations
of OpenFormula?  I know about dwheeler's yacc and lex parser for it, but
I'm also interested in an execution engine.  I'm not willing to try to
disinter this from a full spreadsheet program, never mind an office suite,
unless there is one that implements its engine in a very modular way.
A small-group evaluator would suffice, at least for now.

-- 
John Cowan     http://ccil.org/~cowan
It's the old, old story.  Droid meets droid.  Droid becomes chameleon.
Droid loses chameleon, chameleon becomes blob, droid gets blob back
again.  It's a classic tale.  --Kryten, Red Dwarf