100% legal to do and his right to do so is guaranteed under Copyright Law
Surreal is not above the law. Surreal has no say in it. If the individual wants to sell their copy of BlitzPlay and transfer all rights to it, there is nothing Surreal can do. Daze legally has this right.
A good example of how wrong this is, is 3DStudio MAX.
When you pay for it, you pay for a licence, not a copy of the software. The licence is not transferrable to another person. That's why you should never buy a used 3D Studio.
It depends on the licence that comes with the software, but the author certanly can specify that his software is sold with a non-tranferrable licence if he wants to.