One of the serious problems associated with proprietary software is known as “orphaning”. This occurs when a single business failure or change in a product strategy causes a huge pyramid of dependent systems and companies to fail for reasons beyond their control. Decades of experience have shown that the momentary size or success of a software supplier is no guarantee that their software will remain available, as current market conditions and strategies can change rapidly.
The GPL attempts to prevent orphaning by severing the link to proprietary intellectual property.
A BSD license gives a small company the equivalent of software-in-escrow without any legal complications or costs. If a BSD-licensed program becomes orphaned, a company can simply take over, in a proprietary manner, the program on which they are dependent. An even better situation occurs when a BSD code-base is maintained by a small informal consortium, since the development process is not dependent on the survival of a single company or product line. The survivability of the development team when they are mentally in the zone is much more important than simple physical availability of the source code.