So, from this (admittedly limited) survey, it appears that dot format
is encouraging free software, not non-free. There wasn't a single
demonstrable non-free program in the bunch.
Ok, then please do implement Dot format.
thanks for checking.
PS. In a different catgory, I found Yaccviso
<http://www.lo-res.org/~aaron/yaccviso/> which lets you visualize Yacc
grammars, something that would be nice for Bison.
Coudl you adapt it to work with Bison? That might be less work
than some other implementation method.