[nerdponx]

But after looking at the source code we found a fatal flaw in this tool: it used Graphviz — a decades old tool written in plain C and compiled to unreadable JavaScript using Emscripten.

Are the "decades old" and "plain C" aspects supposed to be bad things? It seems like the real problem is "compiled to unreadable JavaScript". Graphviz is a great example of "if it ain't broke, don't fix it".

[ryandrake]

"Decades old" often means that it is mature, has relatively few bugs, and is not going to soon go through some major API-breaking re-architecture just because the maintainer wants to experiment with a new framework-of-the-week. "Written in plain C" means I will likely be able to call/integrate it into my project with little fuss. These are both things to actively look for when browsing for open source libraries.