>> I saved seeds from a Proven Winners variety, and it comes back true every year. (Shhh....don't report me to the Proven Winners people)
The way I read things, it is only "asexual propagation" that plant patents or "prpagation prohibited" make illegal.
Anything with the word "seeds" in it is sexual propagation, and we're always free to do that.
I think it was part of the legal definition of what they had to do to get a patent: propagate sexually and select the offspring. That counts tpwards developing a new strain, and experimenting.
So the descendents of seeds you produced are your own strains, and you can propagate those all you want.
I think it might not be very considerate to market your strains in heavy competition with the original developers, until you developed something distinguishable from their strain. After all, they have to make back their investment or they won't develop many more new strains.