Krzysztof Kosiński authored May 07, 2016 and Krzysztof Kosiński committed May 07, 2016

Most Inkscape source code does not specify GPL version, so it is essentially
GPL v1+ under section 9. Authors of the few GPL v2 only files were contacted
and all agreed to relicense under GPL v2 or later. We also have a few files
copies from GIMP, which are GPL v3+, so the complete program is available
under GPL v3 or later.

(bzr r14873)