gtk.org, the active and current homepage of GTK+, says right there on the homepage: > GTK+ is free software and part of the GNU Project. GTK+ development does

gtk.org, the active and current homepage of GTK+, says right there on the homepage: > GTK+ is free software and part of the GNU Project. GTK+ development does take place on gitlab.gnome.org, but it is still part of GNU (unlike the rest of GNOME, which did start out as part of GNU, but hasn't been run by GNU for years and years).