RepRap and Open Source

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[reprap-dev-policy] RepRap and Open Source
Adrian Bowyer adrian.reprap at Sun Feb 6 08:08:35 PST 2011

My purpose in this post is to say why RepRap is, and always will be, Open Source.

Eccentrically, given that purpose, I shall start with a completely irrelevant fact: I think that Open Source is a good thing. If I ruled the world (which, fortunately for the world and - more importantly - fortunately for me, I don't), all engineering projects from the writing of bank software to the construction of nuclear power stations would be run in an Open Source way. Given my approval of Open Source, you might imagine that that was the reason that I chose it for RepRap.

Not so.

Even if I thought that Open Source was an evil pinko conspiracy to undermine capitalism, to destroy healthy competition, and to usurp the perfect system of intellectual property rights given to humanity for all time by God when he wrote them on stone tablets at Mount Sinai, I would still have made RepRap Open Source.

The good moral and political arguments for Open Source are inconsequential as far as RepRap is concerned, and RepRap is not Open Source because of them.

Remember that RepRap is not about 3D printing. It is about replication. The purpose of the RepRap Project is to make a useful self-replicating machine. We just happen to be using 3D printing to do that, because it is currently the most appropriate technology to achieve our ends. But we could equally imagine a self-replicating laser-cutter. Indeed, many people on the RepRap Project are also working on precisely that.

Ask yourself: which will be the more numerous 3D printer (or laser cutter): one that can self-replicate, or one that has to be made in a conventional factory?

Then ask yourself: which will be the more numerous replicator: one for which all the plans are freely available, or one for which the plans are hidden?

RepRap is Open Source because Darwinian game-theoretic analysis says that Open Source is an evolutionarily-stable strategy for a useful replicating machine that is intended to maximise its numbers in the world. This is a completely amoral fact, and it is the reason that I made RepRap Open Source. RepRap is Open Source because that strategy must out-compete closed-source systems in reproductive fitness.

Some of you may think that I am rather lax in my pursuit of those people who would appropriate RepRap technology and close it off, thereby breaking the terms of the GPL. The reason that I am lax (and I am) is because I don't care about those people. I don't care about them because I know that by closing off the path that they have chosen, they have turned it into a reproductive cul de sac; they have made their machine sterile.

If I am lax, others may be more attentive. This post is in no way intended to instruct, or even to request, others to act or to see things as I do. In particular, RepRap developers retain the copyright in their own developments, and may wish to enforce licencing with more rigour than I. Go to it, I say. I merely started this project; I would be alarmed and upset if I were to find my subsequent actions (or lack of them) taken as a prescriptive model.


Every RepRap can make RepRaps. Also, every closed-source 3D printer, and every non-replicating 3D printer, can make RepRaps. But RepRap won't make any of them. The exponential mathematics of the RepRap population against the rest follows inexorably. Chasing licence infringers will make almost no difference.

If you are taking part in the RepRap project, then I hope that you believe Open Source to be a morally and politically good thing, as I do. But if you don't believe that, you are still welcome to take part, by me at least. When it comes to the success or failure of RepRap, moral beliefs are almost completely irrelevant.

It is the evolutionary game theory that matters.

Best wishes


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