Well, some one may know about GPL. But there is also a LGPL, MIT license, they both seem to be similar to GPL. Do you know what are the differences among them? and you know what is freeware?
I just get a license chart from the AWStats(a webpage statistics programe,which our blogwind uses) project website. Maybe you can get some basic information from it:



 
if you think this is all about it, you are wrong! there are benchs of different licenses that derive from the GPL. You may take a look at this page on Open Source Initiative Website.