It appears that Adobe is going down the path of charging a subscription for their software (instead of an artist being able to buy it outright). So you never really "own" the software. You are merely renting it.
If you are like me, you are not a fan of subscriptions. I believe you should be able to resell it or give it away when you are finished with it, as long as you follow the licensing guidelines.
Here are 10 free alternatives on the Gizmodo website. Read about them here: http://gizmodo.com/5974500/10-photoshop-alternatives-that-are-totally-free