MultiBoot USB
This is a project that contains a collection of GRUB files and scripts that will allow you to create a pendrive capable of booting different ISO files.
KolibriOS is a tiny open-source operating system with a monolithic preemptive kernel and video drivers for 32-bit x86 architecture computers. KolibriOS is a fork of MenuetOS, written entirely in FASM (assembly language). However, C, C++, Free Pascal, Forth, among other high-level languages and compilers, can also be used in application development. KolibriOS features a rich set of applications that include a word processor, image viewer, graphical editor, web browser, and over 30 games.