Jlo is sometimes referred to as a booty loader.
Jlo is simple, easy to understand, and mostly written in C. It runs in the 16-bit real mode of the x86 processor and is built using the BCC C-compiler for 16-bit cde.
One nice feature is that system updates can be done as an atomic operation. New software can be downloaded into the boot device over an unreliable link. After the software is downloaded and verified, a single bit is written in the boot sector to switch to the new software. This makes for a very narrow window where the system might be made unstable be a software update.
This boot loaded is used by the Galfa Spectrometer and a few other commercial embedded systems.
Jlo is getting kind of old, it's intended to be used with cramfs root filesystems and I think it has only been used with 2.4.x Linux kernels