Software licenses are generally considered to be contracts. A copyright, meanwhile, is not a contract. Instead, it avails the creator of intellectual property of the protection of copyright law, which is limited to the life of the author plus 70 years, by which time the author is likely to be concerned with other things. All one needs to do is to create the work in a recognized medium, though being able to prove that one created it and when it was created is not a bad idea. Under copyright, no one may, really, do anything with your work without your permission.
Contracts are customarily the means whereby that permission is granted.
Though third parties may receive benefits of a contract, they cannot become obligated by one. And here is where the chafing begins. But what is most significant about the agreement is that it purports to restrict subsequent transferees who receive software from a licensee, presumably even if the licensee fails to attach a copy of the agreement. As this new transferee is not in privity with the original copyleft licensor, the stipulation seems unenforceable. This isn't as complicated as it sounds.