History

BIOS

BIOS is the good old, inscrutable way of initializing a hardware platform in the pre-UEFI days. It's a binary blob with no standardized structure, that is responsible for initializing CPU and memory, and jumping to a hard-coded position on the MBR of the first disk drive.

Starting around 2000, BIOS has been largely replaced by the standardized UEFI. Many UEFI implementations still offer a BIOS compatibility mode called CSM (Compatibility Support Module), which makes it behave like an old BIOS.

Note that the term "BIOS" is sometimes misused to refer to the general concept of system firmware, such as UEFI or even LinuxBoot. However, as "BIOS" refers to firmware with specific functionality, UEFI is definitely not a BIOS, nor is LinuxBoot a BIOS in the original sense.

LinuxBIOS

The LinuxBIOS project was created in 1999 by Ron Minnich, Stefan Reinauer and others. It is not much younger than UEFI, but they were already experimenting the idea of running Linux as firmware. Like many great ideas, it was way ahead of its time. At that time Linux was not mature enough to be used in a hardware initialization project, and while LinuxBIOS was successful in several performance-and-reliability critical environments, it didn't see mass adoption.

In 2008 LinuxBIOS became coreboot.

LinuxBoot

NERF

This is the original name for the stripped UEFI, plus Linux, plus u-root. The name stands for Non-Extensible Reduced Firmware, as opposed to UEFI's Unified Extensible Firmware Interface. Basically, saying that NERF is an UEFI replacement that prefers to be more compact, less extensible, and a bit more opinionated. While extensibility is nice and often desirable, too much extensibility and too many "yes" can make a complex project very hard to maintain and keep secure.

NERF was created by Ron Minnich while at Google in 2017. The project grew and was maintained by Google's "NERF team".

NERF eventually became the linuxboot build system.

Heads

Heads is an open source firmware for laptops and servers created by Trammell Hudson (a.k.a. osreasrch), aimed at strong platform security. It is currently maintained by Thierry Laurion.

Open Platform Firmware

Open Platform Firmware (OPF), formerly Open System Firmware (OSF), is an official subproject of the Open Compute Project (OCP). OPF has been developed in the open, by various members of OCP that were interested in having open source system firmware. OPF defines a set of guidelines with contributions from Microsoft, Google, Facebook, Intel, 9elements, Two Sigma, and several other companies.

The important thing to keep in mind is that Open Platform Firmware is a project name, not an implementation, nor an idea. An implementation (like LinuxBoot or OpenEDK2) can be OPF-compliant if it follows the aforementioned guidelines.

Currently, Open Platform Firmware has two work streams:

LinuxBoot, led by Google, Facebook, 9elements, ITRenew, TwoSigma, and others
OpenEDK II, led by Microsoft and Intel