If I write some decent software, how will I make money on it?
license-types of some specific tools I might use (key issue: how "viral"?)
Py Thon: GPL-compatible GPL-compatible doesn't mean that we're distributing Python under the GPL. All Python licenses, unlike the GPL, let you distribute a modified version without making your changes Open Source. The GPL-compatible licenses make it possible to combine Python with other software that is released under the GPL; the others don't.
e4graph: BSD Open Source