Well it's an option - either you follow the terms of the license agreement and give up ownership, or you're in violation of their copyright. (Or you contact them and work out better terms.) They can put any terms they want in the license agreement, if you don't agree to them you don't get a license.
Think of it with money instead. If they charge $20 for a license, then you have the option to pay, or to be in violation of copyright. Here they're requiring a transfer of IP instead of money but it's the same deal.
