Patents still apply to open source, even if they are not selling anything.

Wait wait, what? When you file for a patent, you make your invention known. In detail. With plans. That's public. The idea being that if somebody uses your designs, they pay you a reasonable licensing fee.

These are just plans. Even if they incorporate patented designs, those designs are public knowledge. It's the use and implementation of those designs that's restricted.

Am I missing something?

Yes. Anyone building or using one of these would be open to a patent suit (if it violates any patents). There is no patent equivilant to "fair use".

>Anyone building //

In the UKPA Section 60(5)(a), (b) says:

An act which, apart from this subsection, would constitute an infringement of a patent for an invention shall not do so if - (a) it is done privately and for purposes which are not commercial; (b) it is done for experimental purposes relating to the subject-matter of the invention; ...

There are other clauses too, for example allowing farmers to use the products of plants they've acquired lawfully.

35 USC 271 has some very limited exceptions too (research related to pharmaceuticals is one IIRC).

It's funny that in the US there is such liberty for copyright but patents seem to be locked down relative to other jurisdictions. I assume you're talking about USA, no one ever seems to note despite it being crucial in discussions of law.

How does that work? Genuinely curious - can a patent holder force someone to un-publish source code?

That's pretty much what happened when a Dutch developer tried to publish source code emulating what the Shazam song-recognition app did: https://www.techdirt.com/articles/20100708/04230710128.shtml

In the USA if you knowingly violate a patent you will be responsible for triple damages. For software that would be 3X the revenue generated. This is true even if the violator does not charge - because the person with the patent is still suffering damages (lost revenue). So practically they can force you to remove it if they can show damages - which wouldn't be that hard to show in the Shazam example.

A court can order someone to stop publishing source code and to pay damages for illegally distributed material.

In the related field of copyright, courts have been known to order the destruction of books, fake watches, etc.

Inducement, etc

See, e.g., http://www.law.cornell.edu/wex/inducement_of_infringement

I think individuals can create projects for personal use which use a patent so long as its only for personal use and is not used commercially or sold.

False. This is a common misconception. There is also no "academic exemption" to patent infringement.

I agree that GP is dangerously wrong about noncommercial use in general, but doesn't the research exemption[1] muddy the waters a little?

[1] http://en.wikipedia.org/wiki/Research_exemption

No. It is very very limited.

That is true in the USA. In the UK, for example, there is an academic exemption. Practically there would be very little damages that could be shown by infringing a patent once in a lab.

"Patents do not prevent "making". They prevent making for another's use. One can make and use anything (well, anything legal, I'm not talking about devices which are themselves illegal)." - Mike McCarty

Patents are for commercial use. This is just publishing the details of construction - anybody can make and use such a device for their personal use, despite any patents that exist.