When talking about open source, many people's first thought is the GNU General Public License (GPL). While the software world has been revolutionised by GPL, the hardware world has seen little change. 

In the open hardware world, one means of achieving "openness" involves sharing design specifications under a license such as the Creative Commons Attribution-ShareAlike (CC BY-SA) license. CC BY-SA lets others remix, tweak, and build upon your work even for commercial purposes. This license is often compared to 'copyleft' free and open source software licenses. All new works based on your work will carry essentially the same license, so any derivatives will also allow commercial use. CC BY-SA is the license used by Wikipedia....Read more at OpenSource.com