Most of the icons in the Legacy theme are from the original GIMP icons.
License is mostly unknown which means that unlike proven otherwise (e.g.
when finding a commit message giving a specific license), they are
assumed to be the default license of GIMP, i.e. GPLv3+.

Most vector versions were done by Denis Rangelov, based on the raster
original versions. Licensing stays the same, with Denis added as
co-author when relevant.

gimp-tool-pencil.svg and gimp-tool-color-picker.svg are taken from the
Inkscape Tango icon theme. Mc from the Inkscape project says that
everything they ship is either GPLv2+ or CC by-sa.

Some icons are modified from the Default icon theme, so licensing of the
Default theme applies: gimp-tool-bucket-fill, gimp-tool-cage,
gimp-tool-handle-transform, gimp-tool-paintbrush, gimp-tool-smudge,
gimp-tool-text.

The icon gimp-tool-measure already existed as SVG before the full
vectorization and metadata shows it as CC by-sa 2.0 by Ulisse Perusin.

When attributing the artwork, "GIMP team" is enough for icons which were fully
created for GIMP. For icons taken and modified from other teams, such as
Inkscape, attribute them for instance to "Inkscape team" and "GIMP team".

Please link to https://www.gimp.org/ where available.
