"Homebrew developer Phobox has released myBootLogo 1.0, a plugin that lets you run a custom gameboot from your memory stick.
The plugin also "avoid the logo "psp" to be shown during the gameboot". I think this means it also unbrands the PSP logo so it doesn't show up over your custom gameboot. Web translations suck.
It's a prx so this should be a safer way to enable custom gameboots instead of flashing to flash0. Check it out. The download's below."