Linux Journal: Software Licenses
"...Brian Behlendorf posted something I hadn't previously thought about. His point, using Apache as an example which is under the BSD license, is the fact that the license, while allowing a proprietary fork in the code, does not allow the use of the Apache name." ...under the BSD license... allowing a proprietary fork in the code, does not allow the use of the Apache name.
"For something new to the market, this probably doesn't matter. But, once your product is established, the name becomes very important. Having a web server that works like Apache is much less important than having a web server you can call Apache in today's market."
"A second interesting issue that was raised in this same discussion is how the licensing of Perl made it possible for Perl (and Python) support to be added to the Microsoft Visual suite. Before you panic, this is not MS-Perl; it is a development environment."