Your project MUST
Allow anyone to study, modify, distribute, make, and sell the hardware.
Provide publicly accessible design files and documentation (the source).
Clearly specify what portion of the design, if not all, is being released under the license.
Not imply that derivatives are manufactured, sold, warrantied, or otherwise sanctioned by the original designer.
Not use the trademarks of other companies without permission.
Not be released as non-commercial or no derivatives.
Your project MAY
Require attribution be given.
Use the open source hardware logo to signify their hardware follows the open source hardware definition.
Require derived works to carry a different name or version number from the original design.
Be copied directly or have derivitives created from it.
Require a viral license.