are "open source" yacht designs a thing

TIL a finished boat plan is more complicated that linux

 

Following on from what Gonzo said, the engineering equivalent of open source is the engineering "cookbook". Gerr's Boat Strength is one example. You don't have to be an engineer to get the engineering reasonably correct. But just as with real cookbooks, just because you own one doesn't mean you are a cook. It takes practice, and a concrete notion of what the result is supposed to be.