PSP/Steins Gate Translation
One interesting example that shows how PSP translation works is the abandoned Steins;Gate PSP translation project.
Note that this patch was never finished, and is meant to be used as a proof of concept to train PSP translators (it is certainly possible to finish it, though).
If you want to play Steins;Gate in English, a official translation was released for PC on March 2014. If you are interested in playing a portable version of Steins;Gate, an official PS Vita English version was released in 2015.
Riku's Script Development Kit
Riku managed to hack the script to inject text without any text reflow issues. He managed to translate a whole prologue, but did not continue the effort due to lack of interest and assistance.
He provided a Script Development Kit with a Proof-of-Concept patch of the first chapter. Someone should investigate how it works, and possibly apply it to the rest of the PSP game to create a perfect patch. Documentation is sparse, but it should just be a matter of trial and error.
For informational purposes only
- I opened the ISO with UMDgen, extracted the Data0.AFS with the AFS explorer, looked out for the .BINs (the scripts) and changed them with a program called sakura (a hex/text editor in japanese), saved, and repacked everything.
Unfortunately, it can be much more complicated than that, since the textbox often has a character limit per dialogue box. This will take some crazy bitbanging haxx to overcome.
- I tried translating the game myself (aka opening the ISO and swapping the japanese text with Shourai's translation), but ran into one major problem: the character limit. Every dialogue box accepts only a set amount of characters; the first line of dialogue works fine, but every following line is missing the first few letters (and at some point, the game just crashes). I don't know shit about coding and Google couldn't help me either, so it's pretty much hopeless.