on RISC OS 5 via an emulator called Aemulor, since the ARMv5 XScale processor does not support 26-bit addressing modes. Likewise, RISC OS 5 itself had to be ported to run properly on the new CPU, and abstraction of the graphics and other hardware interfaces created, to allow it, for example, to use standard graphics cards, instead of Acorn's own VIDC chip. In July 2003, Castle Technology Ltd bought the head licence for RISC OS from Pace Micro. Shared Source Initiative In October 2006, Castle Technology Ltd announced a plan to release elements of RISC OS 5 under a source sharing license. The Shared Source Initiative (SSI) was a joint venture between Castle and RISC OS Open Limited (ROOL), a newly formed software development company, which aimed to accelerate development and encourage uptake of the OS. Under the custom dual license, released source was freely available and could be modified and redistributed without royalty for non-commercial use, while commercial usage incurred a per-unit license fee to Castle. The SSI made phased releases of source code, starting in May 2007. By October 2008, enough source was released to build an almost complete Iyonix ROM image. By late 2011, it was possible to build complete ROM images from the published sources; with the full source code available as tarballs, CVS, or a web interface to the CVS archive. In October 2018, the rights to RISC OS 5 were acquired by RISC OS Developments, and re-licensed under the Apache 2.0 license. ROOL continues to maintain the source tree and co-ordinates an international developer community on a non-profit basis to support and encourage development. Prebuilt images are available, as both stable releases and development "nightly builds". Ports of RISC OS 5 are available for the A7000/A7000+, RiscPC, RPCemu, the OMAP3 BeagleBoard and derivatives, OMAP4 PandaBoard and PandaBoard ES, AM5728 Titanium, the Raspberry Pi, and the XScale Iyonix. References External links Archiology: Michael Gilbert's collection of "relics from Acorn's past" Arthur Lives!: a guide by Ben Jefferys Arthur OS Emulator What is RISC OS? Pink Noise Productions OS documentation RISC OS History of software