McZonk posted this news:

I have written a short tutorial about how to use the psp osk. So you don't have to crawl to Quake 2 source. It is pretty easy if you follow some basics. But it is unfinished, because I have no idea about settings a specific char set and all the other stuff. So the half of the struct is used is unknown.
Download: http://zcom.sytes.net/tee/tutorials/psposk/psposk.zip
I will give it to pspdev.org to include in the pspsdk.