Every license restricts things, except maybe a CC public domain license. BSD imposes 3 conditions on distribution, the GPL numerous. My proposed BSD+ is not nearly as restrictive as the GPL. In addition to the 3 conditions of BSD, it just forces BSD-incompatible licenses such as the GPL to dual license.Besides, what you're trying to do is accomplish the GPL there without trying to "restrict" things. Unfortunately, there is a reason that many GPLed projects are flourishing and many of the BSD licensed ones are not. If you ponder for a moment why that might be, you might understand things better. You might not wholly agree with the tenets, but there IS something to it all.