While the demo itself isn't new, the ability to download it is. For those who haven't yet bought the "Outstanding" game, nor were lucky enough to get their hands on the UMD demo disc, it's now available for download on the Killzone: Liberation website.
The demo is the same as the UMD disc, though may be more helpful for those who wish to play two-player ad-hoc. The only downside: The downloadable demo requires firmware 3.02. I suppose this isn't a huge deal, as those of you who can now downgrade probably have (or will be), and could therefore use DevHook, or the infamous 3.02OE firmware anyways.
Via PSP-Vault