Hi, I'm just building new metadata for Fedora, and noticed that you've included an AppData file -- thanks! Unfortunately it doesn't validate -- <licence>GPL-2</licence> -- this is supposed to be a valid SPDX license (and we suggest a content license rather than a code license). See this page for more details: http://people.freedesktop.org/~hughsient/appdata/#metadata_license
The simplest thing would be to just do s/GPL-2/GPL-2.0 -- thanks! Richard