[bkor]

Suggest to just ask various distributions nicely if they could package xdg-app. Especially the ones that you target and/or use frequently. I quite like the idea behind xdg-app and I've packaged xdg-app for Mageia Cauldron (think Fedora rawhide). As I did that only yesterday I don't know if it works. But next stable release of Mageia will have it.

http://pkgs.org/search/xdg-app

Apparently only available on Fedora, openSUSE and Mageia at the moment.