If you are interested in contributing to Servo. I also recommend the talk "Servo and You: a beginners to contributing to Servo" given by Josh Matthews at FOSDEM a couple of months ago. You can find the video here:

http://mirrors.dotsrc.org/fosdem/2015/devroom-mozilla/ud2218...

Perhaps I am not reading the correct area, but is there a legend for the different issue tags and what they all mean?

I'm not aware of one but there might be something in the Servo wiki.

I have - tried to - read some posts by doublec where the topic is programming in the ATS lang. But he apparently also likes to dip his feet in simpler languages like Rust. (:P)

Haha, yes I'm a big fan of ATS and I use it in projects. What motivates the dabbling in Rust is that it'll be possible at some point to use Rust in Gecko, and Servo is an interesting project to contribute to.

I'm currently reading all your old posts on factor. It's so sad that it seems almost dead, it's incredibly good and mind bending. Have you lost interest for this language ?

Factor is still maintained and there is activity in the mailing list. I still use it. Recently I restored from backup an old project of mine that is written in factor, http://tinyvid.tv. It was fun hacking on it again - reminded me of what a great language it is.