I used it once and really liked it. There is a geometric modeling editor GUI called `mged`. But in general you define your model based on textual input. BRL-CAD has its own DSL. To get a feeling, have a look on the reference card: http://brlcad.org/w/images/5/52/MGED_Quick_Reference_Card.pd...

I would say that this is not a tool for everyone, but everone who appreciates time-proven UNIX principles & tooling could find a hidden gem here.

could you compare to other common, current CAD-systems? From what I got out of the it, it's focussed on bridging between pure CAD and analysis (e.g. focus on meshes over geometry construction).

Does it have an assembly module?

From what I get from it, it's more similar contemporary (80ies) CAD systems. Once found a manual for EUCLID in my fathers engineering time-stuff and it looked similar.

No, I can't really compare. Back then, I needed to model a not too complicated geometry for some scientific programming applying raytracing to calculate some view factors. BRL-CAD provided all the tools I wanted (raytracing with `nirt` command: http://brlcad.org/w/images/f/fe/Interactive_Raytracing_-_The...) and I could finish that job in quite short time, this was really nice. But I have no wider CAD experience.

Is it a good alternative to OpenSCAD then?

screenshots at http://brlcad.org/gallery/index.php?/category/12