High Quality Content by WIKIPEDIA articles! Little John PalmOS (or LJP in short) is an open source multi-system emulator for Palm OS 5.0 (or newer) devices. The program emulates ten game consoles or handheld devices for Palm OS, and will open standard ROMs stored on the device or memory card. Note that, unlike most emulators for a mobile device which emulate the mobile device itself on a Windows, Mac OS, or Linux platform, LJP runs on a Palm OS device to emulate game systems. It is free software licensed under the GPL.