So to some extent, to work on it probably does require bashing against some theory for a while. I don't mind that, but on the other hand I don't want to get stuck *only* in theory.
It also depends on the part of the pipeline that you're interested in. There's quite a difference between, say, the typechecker, and the codegen stages, and they require rather different knowledge. I'm aware of that. Right now I'd like to get a general understanding of the project. Later I was thinking about looking into concurrency and parallelism and perhaps at some point in the future at the typechecker (I guess this requires lots of theoretical background I don't have).
And this is where I'm a little stuck too. I have a reasonably good picture of GHC's pipeline, having worked on it for my master's thesis, and I'd like to get more involved and possibly even contribute something useful. But I'm not sure where to start. Well, that's a bit discouraging - if you worked on it in master's thesis and still don't know where to start then it this is probably even harder than I suspected.
Janek