Corel Aftershot Pro (photo managing/editing software is currently free @ Amazon.com
I don't have time to test this and render an opinion right now, but it's from a recognizable company and linux compatible and it's free with the coupon code "MACR0913" ($15 off digital software download, no minimum, one usage per account): http://www.amazon.com/Corel-AfterSho...DE4/ref=sr_1_1 It specifically mentions Ubuntu compatibility.
I'm not affiliated with either Amazon or Corel, nor do I have any particular antipathy towards any open source equivalents that may exist.
Re: Corel Aftershot Pro (photo managing/editing software is currently free @ Amazon.c
It does say that but the price says 12.99 for the Mac download only and there isn't an Ubuntu option or Linux etc. Is the key tied to a specific OS version of the program do you think?