Here's a port I have made of ps2yabasic to the PSP. It lets you play (but not edit) all your yabasic saves on the PSP.

I've included eboots for both 1.5 and 1.0 BIOS versions - put the correct folder(s) in the PSP/GAME folder on the memory stick.
Put the yabasic folder in the PSP folder on the memory stick.

What's working?
Pretty much everything except below!

What isn't working?
It runs about 80% of the speed of the PSP.
The console output window doesn't work.
No text input is working.
Slight memory leaks.
The beep doesn't work.

Things to note:
It slaps the PSP into 333MHz mode while the interpreter is running, and back into 222MHz mode at exit.

Press both shoulder buttons together to exit the interpreter.