Well it is silly, but what actually is a life sentence in the US? A life sentence in the UK is usually 30 years I believe, and not actually until you die. Sometimes you can get out in half of that time depending on the parole setting but many life sentences carry a 'minimum' term of 15 years and you can get out after that due to good behaviour or whatever.
'Life' in the UK has only meant life in less than 100 or so cases. You'd have to be Satan personified to get it.
In the US life without parole means exactly that which is what he got. They seem awful keen to dole those sentences out too. Contrast that with Norway where it's not possible to serve more than 21 years. They'll probably have to come up with some interesting ideas to deal with that charming Breivik character.