Well, let's thank aD (rip) for making acs package-based... acs-workflow is the package that depends on graphviz; I would say "this makes acs-workflow less useful than if it operated in a completely-free manner, but it doesn't necessarily make the package non-free, and it certainly wouldn't affect all of openacs".
In the invocation of the shell command which invoked graphviz (in response to me saying "show me a workflow"), I saw a command line option that said "generate a gif", so it's at least a potentiality that graphviz can generate such as PNGs. That might get us somewhere :)
IBM thinks graphviz might be free (there's a letter posted by IBM on some planet that said this.)
Conventional wisdom suggests that a piece of software can be free if it depends on a not-free thing but is in all other aspects free (as def'd by GPL)...
Having said that, we can also say this would limit its usefulness in a free environment.
Should we act on this? I think -yes-, and if there's an easy way to get graphviz to generate PNGs, I think we should fix it today.
A replacement for graphviz itself is of course a harder problem, so let's separate the hard from the easy, do the easy part now, and start working on the hard part.
