Good bug report 
The quit menu entry has been fixed in git, the filtering of games is something I have to look into, hopefully I’ll have a fix for next version.
Lastly, the credit / license problem in the about dialog is related to the desktop environment currently running, on Gnome Shell or Budgie, the about dialog is different than on XFCE or Unity and doesn’t have that problem. Also, it’s the default About dialog for the Gtk framework so there’s not much we can do to change it.