It doesn't use multiboot, it uses its own bootloader.
It uses the echidnaFS filesystem.
Get its tools by using make fstools

To compile this repo you need a cross GCC compiler.
Get it here

1. Get the cross compiler
2. Use make fstools to make echidnaFS'es tools
3. Use make to compile the OS

The image os.img is QEMU bootable out-of-the-box, so just use

qemu-system-i386 os.img

I also included a bochsrc if you need a debugger.