I'm eager to hear what he says!

The Constitutional purpose of the US patent system is to promote the progress of science and the useful arts, so discussing how to practice or improve patented inventions is definitely legal. (That's why patents are published in the first place.) That's what Adrian was doing. There's no "personal use" exemption in the US law, but there is an exemption (in caselaw) for research, although a court decision around that time narrowed it substantially. It would be impractical to practice a patented invention for such protected research purposes if the law prohibited you from even discussing how to practice it. But in fact you can even go so far as to patent an improvement on somebody else's patented invention.

There is a prohibition on inducing others to violate a patent, but generally it's applied in cases where someone is selling a nominally-non-infringing product whose only real use is to practice the patented invention.

I agree that, at the much later time that MakerBot not only existed but had turned evil, its patents had a chilling effect. I can absolutely confirm that! But at that point the cat was already out of the bag, and the original FDM patent had already expired, so that particular patent no longer had such an effect.

The question I intended to discuss (because in my interpretation it's what superconduct123 was asking) is why we didn't get something like the Prusa Mendel V2 in 01980 or 01990 or 02000 instead of 02010. Obviously the concerns people had about patents after 02010 aren't the reason; if it was a chilling effect from patents, it would have had to be a chilling effect much earlier than that.

And I don't think it was. We could imagine a history where there was a low-cost open-source design in 01990 or 01995 or 02000 or 02005 which companies couldn't mass-produce because of the patent, but that isn't the history we actually got. Why not?

I think the answer is basically that a low-cost 3-D printer sounded like such a crazy idea that none of the small number of people who even understood the concept of a 3-D printer decided to dedicate the effort necessary to make it happen. Also, everything was much more difficult then. I think Adrian accelerated the timeline by 2–5 years.

But only 2–5 years. Fab@home or the (non-FDM!) Open3DP group at the University of Washington would probably have been successful without him. MIT started their Center for Bits & Atoms in 02001, and they started up their first "Fab Lab" that year. EMSL built their Candyfab 4000 in 02006, which was the first 3-D printer I saw actually operating (at TechShop, if I recall correctly). So the memes were spreading.

But basically I think you could have built a hobbyist 3-D printer in the 01980s if you'd realized it was a good idea. Just as you could have built a submarine in the 01600s. The necessary technology was available. It would have been enormously more difficult, especially before the advent of cheap PIC16s in the 90s. Finding like-minded people on GEnie or FidoNet would have been much more difficult than in the blogosphere. 3-D modeling in 512KiB of RAM at 1 MIPS would have been limited. But you could have done it.

The question I'm most interested in here is: what similar opportunities are we missing today?