The Pidgin installer auto-downloads and auto-installs Gtk libraries, and Pidgin has always run flawlessly for me on Windows. What aspect of Gtk is temperamental to install on Windows machines?
On my Linux distro, I can import gtk in Python 2.7 but can't in Python 3.x without enabling 2.x support. I can, however, import Tkinter in both. I should ask my distro's maintainers why that is so, unless python.org would be more likely to know.
Meh I had a look at LGPL and it looks like just a way to permit a client or employer to make your work proprietary so the GPL no longer affects it. Might as well make your own code proprietary to you and sell a license to use it, if you're going to do that--although I strongly doubt that commercial software companies will permit you to retain control over rights to the code you write for them.