Import of gtkwave 3.3.104 from sourceforge.
See it on guix.gnu.org, where it links to sourceforge as the site.
Why not? (It weren't on github, so I couldn't fork it. Maybe github is not good for GNU and libre projects…?)
Read the original_README.
Read the Original license. The excerpt shown below clarifies that the LICENSE included should be ok:
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.