Open-source hardware (or open hardware) refers to hardware that is
developed in a manner similar to open-source software. There’s a widely
accepted definition of open-source hardware, but it is probably not as well
known as its open-source-software counterpart. In addition, there is a popular
certification program that hardware makers can use to indicate which of
their devices meets that criteria. But there are some vendors that are
showing more enthusiasm than others in participating in the process—or in
producing
open hardware at all.

Source: LWN.net – [$] Defining open hardware