You can't return opened software.
"You can always return the software..."
This isn't entirely true. Right now many stores WILL NOT ACCEPT returns of opened software packages. CompUSA, for example, will only exchange software for exactly the same title as you've purchased. Not knowing terms of the contract until after the sale is not an option *AT*ALL*. It may also be illegal under federal contract law, which generally trumps state law, but in this case who can be sure that the courts would view it this way.