As of today, Lightroom 4 is now a part of Creative Cloud. If you login to your Adobe Creative Cloud account, you’ll find that you have a license to Lightroom on top of the other applications already in the package.
Both Lightroom and Photoshop are a must for professional photographers, and now both are included making Creative Cloud an even better option for professional photographers.
All Creative Cloud desktop applications come with a license for 2 machines, one for your main machine and one for your backup computer (usually a laptop), though both copies should not be run at the same time. If you already have a license for a retail version of Lightroom 4, then you can disable and move that particular copy to another machine giving you the ability to use more machines at once if you’d like. But the best part is that you won’t have to pay for an upgrade of LR next time, as all desktop applications in Creative Cloud come with free upgrades as long as your a member of Creative Cloud.