An Open Source license is meant to encourage growth rather than restricting it. Each of the tests is motivated by some potential threat to the environment in which software evolves. Required, Permitted . The license for proprietary software typically forbids redistribution of source code. The OSD requires that unrestricted redistribution of source code must be permitted.
Some licenses require it.
Unrestricted, Documented, Separate . Packaging of Modifications specifies how the source code tree will be maintained, and the end users responsibilities to that tree of code. Source code is shared to be modified. Licenses differ on how modifications may be distributed. Some licenses require that at least the modifications be documented.