Could you please stop sending links to sharing sites offering copyrighted software. There is no need to do that. Being unable to wait until the update is available in your local ovi store or being unable to configure the app manager to fetch such info is no excuse for breaking laws.
I didn't get any update notification but when I uninstall my 1.3.4 version and download the game again from the store, it was the new 1.4.2 version (even if, on the store, the text about Angry Birds always talk about the 1.3.4 version).
For PL4, if you can get (legally) the "Angry Birds" package for Palm Pre or Android with all the 1.4.2 levels, you can decompress it and copy the "levels" directory content into "/opt/rovio/angrybirds/data/levels".
After this manipulation, I get all the levels including PL4 in my N900 "Angry Birds" version .