Editing Incubator escapee wiki:FAQ/Copyright (section)

===Permissive licenses===
:[[Permissive licenses]] allow for unrestricted  use, modification, and distribution of a copyrighted work. The  modified [[BSD license]], the [[X11 license]], and the [[MIT license]] are each examples of permissive licenses. These licenses seek to make it as easy as possible to reuse the licensed work: the objective is generally to make the work available and as widely used as possible, but without releasing it to the public domain. Those using permissively licensed works can relicense derivative work under more restrictive license terms. 

:Because of the very limited license requirements, license incompatibility problems with this type of license are relatively uncommon, so it is very easy to reuse these works.