But IIRC it's using the XUL framework which was discontinued by Mozilla

That is one of the many problems of Komodo and why nobody has taken over the maintenance. (Frankly, *any* project depending on the codebase of Mozilla is screwed, there are always random design changes by the foundation popping up that make no sense).

I'm looking at the Dockerfile right now. It starts by requiring Ubuntu 17.04 as a base image, then downgrades gcc 6 to gcc 4...

The build instructions for Linux are just as bad. Not only do you need to use a g++4.9 and Perl 5.22, you also need to (somehow) get a Mozilla version from 2014 running on your system.

True, not everything is ActiveStates fault, their main one is that they trusted the Mozilla foundation to, for once in its existance, do the right thing and provide long time backwards compatibility for XUL, one of their most hyped features at the time.¹

The sad thing is, without a major, major rewrite Komodo IDE is totally dead.

¹ The foundation and its firefox developers are also responsible for WebSQL getting dropped as W3C standard proposal in favor of their awful, idiotic "database" design that's just a key/value store with a badly designed API. This made my life as a web developer significantly harder for many, many years. To say that i'm not a fan is putting it rather mildly...