Open source hardware is a term we've used here on MAKE & CRAFT for describing some of the projects featured as well as some of our electronics kits and it was the subject of a talk we participated in at then SXSW conference, but what is it?
There are a few definitions, some come from "open source software" which is usually considered software's - "source code under a license (or arrangement such as the public domain) that permits users to study, change, and improve the software, and to redistribute it in modified or unmodified form"
So how does this translate to hardware?
Electronic hardware can be divided up into layers, each of which has different document types and licensing concerns.
Hardware (Mechanical) diagrams
Dimensions for enclosures, mechanical subsystems, etc. For 2d models, preferred document type is vector graphics file, with dimension prints, DXF or AI, etc.
Example: Motor-driven screw block from the RepRap 's thermoplast extruder head, an open source 3D printer.