It's GTK+3 now, not GTK+2. The same long description blurb on their homepage
has been changed from GTK+2 to GTK+3 as well.
<name>Gentoo GNOME Desktop</name>
</maintainer>
<longdescription lang="en">
-Subtitle Editor is a GTK+2 tool to edit subtitles for GNU/Linux/*BSD. It can be used for new subtitles or as a tool to transform, edit, correct and refine existing subtitle. This program also shows sound waves, which makes it easier to synchronise subtitles to voices.
+Subtitle Editor is a GTK+3 tool to edit subtitles for GNU/Linux/*BSD. It can be used for new subtitles or as a tool to transform, edit, correct and refine existing subtitle. This program also shows sound waves, which makes it easier to synchronise subtitles to voices.
</longdescription>
</pkgmetadata>