Fanjita posted on his site that he has successfully ported Tetris to firmware v2.5.

Just a small thing, really, but I’ve ported my Tetris game to the GTA exploit, and have it running on a v2.50 PSP. There’s a small technical glitch that means it doesn’t run yet on v2.60, I hope to sort that out ASAP, before I release a version that will run on any firmware that can run GTA. So – no release yet, but it’s imminent.

As well as being the first homebrew game for v2.5 and v2.6, it will also be a good test of the improved GTA loader that will be used to launch the EBOOT loader. Sadly at the moment this is still for US and EU versions of GTA only, my attempts so far with the German version haven’t worked correctly, but I hope to change that soon.

Hopefully this will open the door to full homebrew for 2.5 in the future.