If you intend to make money from license sales you could go with APGL/Commercial dual license. (That will most likely make me stay away until I can justify a commercial license.)
The sole exception I can think of is plug-ins, but that would depend on the implementation.
The only problem is that existing releases will remain under their original terms of release. For example, if you create a release with MIT, that release will remain available under the MIT licensing terms until your copyright of that code expires.
IANAL and all that, of course.
I'm currently working on something related and I could really use this.
May I ask how are you computing the shapes of rectangles? Is there some optimization going on to fit them?
There's no real optimization, everything is just done from the bottom up: a box is large enough to contain its rows, rows are large enough to contain their "cells" (which are just the boxes the next level down).
There is some padding that is fixed, and some (the "handles" on either side of a row) that scales down with depth, though at a different rate than the text which is the main control over box size. Handles disappear entirely first, as it isn't possible to click on a row directly once it gets too small (instead a click will zoom in on the node).
While pinch zooming some effort is made to try to keep focus on the same object, but that's just a matter of keeping the object in the center of the zoom in roughly the same place on screen.
Happy to answer more questions here or by email (agashlin gmail), and I'd love to hear about your project.
Make of it what you will, I find it neat but overwhelming, and this is only 128 definitions.
You may have to tap on the text box to get the edit to work and engage your keyboard, the auto focus seems to work only about half the time on Firefox for Android so I expect it is problematic on various browsers.
Thanks for the feedback!