Creative Commons License
The Creative Commons relates to a licensing model for Open Source Software. It is used by many open hardware developers and covers many but not all the needs of that community as well.
It covers a basic licensing model and then offers optional variations as would suit the creator of the work. The various options are described on the Creative Commons site.
It is a legally binding solution for software that operates on Copyright law which is respected in almost all countries world wide. The enforceability for hardware is untested but considered inadequate as copyright infringement is usually not required to abuse the licence model for hardware designs.
The most common versions used on the RepRap project are