legal: license
What license to use?
Creative commons
Creative commons is a pre-written license. This means you don't have to learn legalese just to publish something. It comes in various pre-made flavors, including any permutation of: attribution, no commercial use, derivative works, modification, and re-distribution. Just attach a copy of your favorite flavor to the bottom of your document, and *kapow* you're set to battle back the impending hordes of litigators. Or so they say.
It looks pretty good. However, I am concerned about whether or not to include the "no commercial use" clause, mainly for the purpose of re-publishing this site in book form. Any publisher will need to charge money for the cost of publishing and distributing the book. Does this violate the "no commercial use" clause? I don't know. I'll have to ask the creative commons people about it.
Pseudo GPL
I (fenn) would prefer something like the GPL, but for documents instead of software. The GPL says that you must provide the source code to any GPL'ed software you distribute, any derivative works are also licensed under the GPL, and also that anyone is allowed to sell or re-distribute GPL'ed software. Ideally "derivative works" in our case would include machines built from plans on this site, so if you sold a machine based on these plans you would have to include the plans with the machine. If you distribute the plans in paper format you would also have to provide the plans in electronic format.
To my knowledge, such a license does not yet exist, so we would have to write it, and verify it with lawyers. However, it still would not have the backing of an organization like the free software foundation.
