Agnix is a small, educational operating system kernel for i386, supporting 32-bit protected memory mode, paging, hardware switched tasks, memory tests, PCI bus, devices, PCI IRQ routing, RT timers, network protocols. It is available with all the source code and is fully compatible with the Linux kernel API.
CD Shell is a scriptable menu system that provides the ability to create interactive multi-boot optical discs. It will make PC-bootable compact discs or DVDs that can select from several program loaders or kernels located on the disc, or boot from other local disk drives that are attached to the system.
Coreboot (formerly known as LinuxBIOS) is a project that aims to replace the normal BIOS with a little bit of hardware initialization and a payload. Payloads can include a compressed Linux kernel, FILO, GRUB2, OpenBIOS, Open Firmware, SmartFirmware, GNUFI (UEFI), Etherboot, ADLO (for booting Windows and OpenBSD), Plan 9, or memtest86.
GAG is a Graphical Boot Manager with a lot of features. It doesn't need a partition, it works with primary and extended partitions in every hard disk, it has a lot of icons, it allows you to put passwords for each operating system, it can swap hard disks and it can be tested from diskette. The SafeBoot feature allows you to boot your hard disk even if GAG is overwritten. It includes extensive support for many languages and keyboard types.
GNU GRUB is a Multiboot loader. It was derived from GRUB. It is an attempt to produce a bootloader for IBM PC-compatible machines that has both the capability to be friendly to beginning or otherwise non-technically interested users and the flexibility to help experts in diverse environments. It is compatible with FreeBSD, NetBSD, OpenBSD and Linux. It supports Windows 9x/NT/2000/XP and OS/2 via chain-loaders. It has a menu interface and a command-line interface.
GRUB for DOS is a rebuild of the GNU GRUB boot manager for DOS, and can be run under real mode DOS. It also has many new features. It can be booted through BOOT.INI of Windows (grldr) and kexec of Linux (grub.exe). It can directly boot NTLDR (WindowsNT/2K/XP), IO.SYS (Windows9x/Me) and KERNEL.SYS (FreeDOS). The disk emulation feature is another enhancement over GNU GRUB, and can be used to run legacy DOS/Windows9x systems with floppy or hard disk images.
Gujin is a PC boot loader that can analyze your partitions and filesystems. It finds the Linux kernel images available, as well as other bootable partitions (for *BSD, MS-DOS, Windows, etc.), files (*.kgz) and bootable disk images (*.bdi), and displays a graphical menu for selecting which system to boot. It boots the Linux kernel using the documented interface, like LILO and GRUB, so it doesn't need any other pre-installed bootloader. It can also directly load gzipped ELF32 or ELF64 files, with a simple interface to collect real-mode BIOS data. There is no need to execute anything after making a new kernel: just copy the kernel image file into the "/boot" directory, with a standard name. Gujin is written almost entirely in C with GCC, and it fully executes in real mode to be as compatible as possible.
HeavenOS is an original, alternative 32-bit operating system for Intel 80386 compatible processors. It is made with NASM (The Netwide Assembler), and is not intended to compare to modern operating systems, but to try to get the best features and discover better ways to do things. It is intended to be a simple and pratical platform for development, running with a small amount of code.