Thank you all for the comments and suggestions. Most of the criticisms are quite fair: graph language improvements, modernization including default styles that aren't from 1980, bring Javascript interfaces like viz.js into the code base, coding multithreaded solvers, etc. Emden Gansner and I left AT&T a few years ago (in my case, it was AT&T's idea not mine) and we have not put a lot of work into the code lately. Emden's done a lot to move the website to gitlab.com that is about ready to go (instead of hosting the site in a VM on a 1.1Ghz Pentium or whatever we left in the rednet closet in AT&T.) We have a small backlog of algorithmic improvements. For instance, Emden implemented Ulrik Brandes' "untangling hairballs" algorithm but it's not in the code base. I realize this is a standard open source refrain, but "if anyone knows how we could support ourselves by working on this, let us know."

Some of the main lessons from this software, which can be applied by other projects:

- For certain applications, people need rich types of diagrams, not just dots and lines. Many automatic tools including ours often still do not reach the quality of the best handmade diagrams.

- We can benefit from using more general systems of constraints, and this area of research deserves further study and exploration.

- Interaction, complex APIs, embedding your software in bigger, more elaborate systems is great, but presents some users with a lot of complication that is too costly to surmount.

- Documenting your work in a way that makes it accessible is as important as the work itself. We did fall short there.

We're grateful we had a good run with graphviz.

Best regards, Stephen North north from graphviz.org