The announcement was made on Desura.com following a two-month beta process.
Desura first launched for Microsoft Windows and then this past summer they began developing the Linux client with GTK+, etc. The Mac OS X client isn't yet out there, but the Linux client has made it.
One interesting item to note is that the Desura client is going to be open-sourced. The server-side portion will remain closed-up, but they'll be opening up the client side to facilitate future developments due to their limited in-house development manpower. Desura doesn't mandate the use of DRM in their clients or other measures, so there shouldn't be any publishers complaining.
Desura can be downloaded at Desura.com where you can fetch the Linux and Windows binaries. Currently there are over five dozen games available on Desura for Linux, with most of them being indie titles but also Unigine OilRush and others.