I don't see why it's any different than a photo-editing app that applies a watermark to the free version. It's intended to let people give the software a try, and if it seems to meet their needs, they buy the actual product.

As for sharing the source code with the NSA, I think you have a better argument there. That said, it's kind of like helping someone install a secure lock on their door to keep out criminals, yet being willing to share a master key with police if it's a matter of life and death.