This was one of pt’s demos during Gnomedex - he showed off this homebrew chess game running on an unmodified U.S. firmware v1.5 PSP.
He also showed off some emulators with thousands of ROMs - you could literally load up your PSP with every Atari, NES, Super NES, or Gameboy game ever made, or use some of the great fan-created ROMs out there.

can you get one for the U.K. firmware 2.00
2.0 firmware hacking is just getting started - people have posted proofs of concept in the last week or so, and it will only be a matter of time until you can run homebrew apps on a 2.0 PSP.