Very Grumpy Bunny has written a post comparing the GPLv2 and the BSD licence and explaining the difference when applied to Amarok.
There are several BSD licenses, so many that you’ll typically see any particular license under BSD terms listed as a BSD-Style license. Example, the Vorbis and Theora codecs. The terms themselves are fairly simple.
#1: Anybody can access the source code
#2: Anybody can copy the source code
#3: Anybody can modify the source code
#4: Anybody can use the source code
#5: Anybody can relicense modified code
Sounds pretty simple, at least compared to the Gnu Public License. Here are the terms of say the GPLv2.
#1: Not everybody can access the source code.
#2: Everybody who can access the source code can copy the source code
#3: Everybody who can access the source code can modify the source code
#4: Everybody who modifies the source code must submit the changes back to the original author
#5: Everybody who modifies the source code must maintain the original license
That does seem a little bit more complex. Immediately we see that the GPL has restrictions placed on what can be done with the code. Ergo, the BSD-style license is more free… or is it?
Read the simplified terms of the BSD-License again. Note anything missing? Well, if you didn’t, here’s what is missing. Any changes that are made to the BSD code don’t have to be given back to the author. Anybody can take a segment of BSD code, do whatever they want with it, and never post any changes back, tell the author what they did, or anything else.
So, there is a critical difference between a BSD license, and a GPL style license. The BSD license adopts a care-free attitude about written software, while a GPL style license enforces restrictions around that software to make sure everybody benefits.
Whole post can be read here.