On June 20, 2006, RISC OS Open Ltd (ROOL) was incorporated with an ambition considered ‘slightly mad’: to turn a proprietary operating system into open software for anyone interested in contributing. Two decades later, the mission has been largely accomplished, and the current RISC OS is in much better health than the one inherited.

To mark the date, ROOL published a retrospective with a highlight for each of the first twenty years, according to the riscosopen.org website. The organization thanked everyone who wrote code, reported bugs, funded bounties, participated in forums and wiki, tested nightly builds, or just cheered from the sidelines.

The early years

In the first year (2006-07), Castle and ROOL announced a shared source initiative in the autumn, and at the following May’s Wakefield Show the first RISC OS sources reached the public. In the second year (2007-08), more parts of the system were released in batches, and ROOL won its second Drobe award, this time for ‘Best demonstration of initiative’.

In 2008-09, a build of RISC OS 5 ran on an IYONIX with a large amount of community-contributed code, presented at the Midlands Show. The following year (2009-10), nightly autobuilds began to recompile and test the sources automatically, while Jeffrey Lee’s port to the BeagleBoard, the first step towards cheap hardware, won an Icon Bar award.

Growth and milestones

The Bounty Scheme, which allows the community to pool donations and vote with their wallets on desired features, emerged in 2010-11 and remains active. In 2011-12, with Piccolo Systems, ROOL published an open SD and MMC file system, providing native support for memory cards on the BeagleBoard.

The year 2012-13 was a watershed: RISC OS Pi brought the system to the Raspberry Pi, a credit-card-sized computer with BBC BASIC at the touch of a key, introducing RISC OS to a new generation. The site’s traffic records did not survive the week.

In 2013-14, RISC OS 5.20 was the first stable ROM release in years, including the Risc PC and A7000 family. To celebrate fifty years of BASIC, the Pico was released, a reduced version that boots straight to the prompt.

Expansion and reopening

Support for the quad-core Raspberry Pi 2 arrived in February 2015, followed by RISC OS 5.22, which included the OMAP4 (PandaBoard) port. In 2015-16, the Titanium, a dual-core Cortex-A15 board, appeared at the London Show, and ROOL completed ten years with most of the original goals achieved.

The following year, a bounty delivered EDID support, allowing RISC OS to read the monitor’s capabilities directly. In 2017-18, the BBC BASIC Reference Manual returned to print, with 520 revised pages, and RISC OS 5.24 came out stable with the Raspberry Pi and Titanium ports.

The big milestone came in 2018-19: with Castle acquired by RISC OS Developments, RISC OS was relicensed under Apache 2.0, free for use, sharing, and modification, commercial or not, for the first time in history.

Modern era and Moonshots

In 2019-20, the port to the Raspberry Pi 4 began, and all the code (106,000 commits) went to a public GitLab. RISC OS 5.28, with official Pi 4 support and about 700 improvements, came out in 2020-21, along with an edition for the Pi 400.

The community awarded 5.28 Best New Development and ROOL’s forums Best Website in 2021-22. In 2022-23, the Archimedes BASIC Compiler began using the floating-point unit, drawing a Mandelbrot 35 times faster. In April 2023, RISC OS was chosen by SpaceX for a Mars mission, a claim that held until April 2.

In 2023-24, native Git client, open SparkFS, and NVMe storage arrived, followed by RISC OS 5.30, which covered seven platforms. In 2024-25, the project surpassed a thousand accepted merge requests since 2019, and ROOL announced Moonshots, a full-time engineering plan to take RISC OS to 64-bit Arm.

In the twentieth year (2025-26), Moonshots gained its first sponsors and volunteers, the total RAM of an 8GB Pi was freed from 32-bit shackles, and Fortran returned to the toolchain after a lost copy resurfaced from an old backup tape.

Looking ahead

ROOL stresses that none of this was the work of the organization alone. Today’s RISC OS is much better than its state in 2006, and the scene around it is more vibrant thanks to everyone who participated. The expectation is to see what the future brings, from the next stable releases to the next steps towards the moon.

‘Thanks to all of you. Here we go for the next twenty years!’, wrote Steve Revill, on behalf of the entire RISC OS Open team.