Update: Looks like the only changes here address security vulnerabilities -- and interestingly, Palm gives a shout-out to Townsend Ladd Harris (a Pre homebrewer no less) who helped find them. Cheers to that.
Update 2: Sadly, Palm's plugged the hole that allowed homebrew apps on the phone without a jailbreak, though software you've already installed on the phone will continue to work. The hole that's been plugged was admittedly dangerous to leave open (installing apps via a link in email), though rooting and installing otherwise remain unchanged as far as we know.
HP webOS 3.0