Read about it here: http://lkml.org/lkml/2010/8/1/188 or a more non-geek friendly description of the changes here: http://kernelnewbies.org/LinuxChanges

It’s nearly 20 years now since Linux first appeared and it’s safe to say that the complexities of the Linux kernel now demonstrate the real significance of what free software is about, what its advantages are, namely, that it has gone well beyond what is possible except through this approach to software.