Some factual errors
There are even more rabid fanboys than I in the RISC OS world, so I'll preempt them (or maybe just warm them up) with a few points:
"Risc", as you point out, is an acronym. Thus it should be RISC. Ditto "RiscOS", which should also be two words: RISC OS. "Rom" should be ROM. Confusingly, the last Acorn machine was the RiscPC (in lower case), but the official logotype has a sort of half-space, so most people write is all joined up as I do. Finally, the mouse buttons on an Acorn machine were referred to as Select, Menu and... Adjust, not "Alter".
There seems to be some confusion about the difference between Lander and Zarch: the former was a demo of the latter. The demo (Lander) shipped with most machines in this era, while the game (Zarch) was a commercial full product. It was exactly the same game on the PC, but known as Virus. The player's ship in that was not triangular (it was non-symmetrically pentagonal), and is the same shape as the Copperhead ship from Bell and Braben's game Elite.
Two final points. First: "Archimedes morphed into the Risc PC line, a series of ARM-based boxes designed to run Windows – on a co-processor, and presented in a Risc OS window." No. Just no. The RISC PC was never *designed* to run Windows - it was designed to run RISC OS natively, and use hardware-based emulation to run Windows within RISC OS. The "co-processor" wasn't a true one in the sense you seem to be inferring; the primary CPU was an ARM610, 710 or some variant of the StrongARM processor, while the secondary CPU was a specially designed 4x86 or 5x86 card which could *only* be used by the emulated copy of Windows. It was also not a default item included with the RiscPC, but usually a seperate purchase.
Finally, there's the fact that you say the line stopped with the death of Acorn/Element 14, without mentioning anything about the two spin-off companies RISC OS Ltd or Castle Ltd. Acorn's demise left RISC OS at 4.02, and ROL/CTL developed this further in two confusingly-numbered parallel brances, known as RISC OS 5 and RISC OS 6 (also known under the names RISC OS Select and RISC OS Adjust). There were also the the Iyonix, the Omega, and some other hardware designed and sold in the post-Acorn era. And last but not least, there are ongoing efforts to port RISC OS to small boards like the BeagleBoard and the Raspberry Pi, these mostly happening through RISC OS Open Ltd (ROOL), a spin-off created when Castle decided to open parts of the RISC OS source.