The problem with this is that there's no legal mechanism to enforce it besides (perhaps!) contract law.<p>If an entity receives the seeds without the contract attached, it can hardly be considered to have agreed to the terms. The providing party may be in breach of contract, but there's no way to bind the receiving entity. A single 'rogue' link in the chain makes it all meaningless.<p>Of course, a variety would have to be truly spectacular for any company to take the effort and PR risk to get involved in that kind of shenanigans, so this approach may have some practical, if not legal, efficacy.<p>Ironically, a potentially stronger way to enforce the license terms would be to... patent the varieties. It's a quagmire of varying rules internationally, though, and there are some exemptions for the use of protected varieties in further breeding of varieties that could then be protected and subject to less 'free' terms. Plants won't ever be subject to the GPL.<p>I'm very sympathetic to the project's aims, but even on a purely ethical basis there is room for argument. If we want more plant varieties to be produced to tackle humanity's next challenges (and... we do), should we not be encouraging companies to make very significant, long-term investments in breeding efforts? It's hard to see how that can happen without some kind of time- and scope-limited intellectual property rights, even if the systems we have now aren't ideal.