Catorise already uses the freedesktop.org categories which are within a .desktop file (it's quicker than looking it up in the package index) if any are present.

It currently only uses the first it finds, but it could use all of them (the standard supports a semi-colon delimited list). I've already played with making Catorise support a comma-separated list of categories in /opt/catorise/menu.

Any future GUI editor for Catorise would be simple to make it support that.