Welcome to Emerald Editor!
To answer your questions:Licensing:
The whole point of the GNU General Public License is about sharing. Essentially you can build any code for Emerald Editor you like - you keep the copyright because you wrote it (that one is part of copyright law in most countries and can't readily be undone). It also means that anyone else who sees your code can look at it, use it, adapt it etc. You still retain copyright over the sections you wrote, but you're allowing other users to modify and rewrite it to work better here.
The slightly thornier issue is about using that code yourself. Of course, for any projects where the result will be licensed similarly, there is no issue. I think I am right, though, in saying that you can use the code yourself for any projects elsewhere that you want - provided that you don't try and claim the first project was in breach of copyright. If I am incorrect about this, please say so.wxStyledTextCtrl:
It should be buildable from the 'contrib' folder of wxWidgets. That said, the build instructions were aimed at wxWidgets 2.6.x - I don't know if wxSTC is still part of it.Structure:
I don't know too much about the physical structure of the EE code as it stands - it's basically a straight import of wxStEdit. The structure works something like this:
|** Operating System **|
|wxWidgets||Interface to OS|
|wxStyledTextControl||wx Container for Scintilla|
|Scintilla||Customisable edit component (includes codebase for syntax highlighting, plus optional code folding)|
It is a little more complex than that but that is the nuts and bolts of it (I'm not a fully fledged C++ programmer so I might have missed a few things in translation. However, a lot of the features that we want to expand will need major rewrites - e.g. with Scintilla the highlighting is built more into the code, while we need it to be from external files.
Soulfish will shortly be getting together a design team to formally wrap the design up and explain it (which may change the above).
Hopefully that should get you started.