If you want a permanently free OS/2 experience but don't need ArcaOS features:
Before we discuss the free aspect, let’s establish why you want this ISO.
ArcaOS 5.1 is not a Linux distribution. It is not a themed version of Windows. It is a direct descendant of the original IBM OS/2 codebase, updated by Arca Noae, LLC. Key features include: arcaos 51 iso free
First, a quick refresher. ArcaOS is the legitimate, commercially supported descendant of IBM OS/2. While Microsoft went the way of Windows NT and Linux took over the server room, OS/2 Warp lived on in ATMs, medical devices, and point-of-sale systems.
ArcaOS 5.1 (released in 2021) is the modernized version. It adds: If you want a permanently free OS/2 experience
It is not abandonware. It is a paid commercial operating system maintained by Arca Noae, LLC.
Will ArcaOS 5.1 ever become free? Probably not in the traditional sense. However, the company has discussed "open-sourcing" abandoned components over time. The kernel itself remains under IBM lock and key. It is not abandonware
If you are a student, retro-enthusiast, or developer, do not be discouraged by the price. Consider the 90-day trial your "free ISO." It costs nothing but an email address and gives you 2,160 hours to explore the object-oriented Workplace Shell.
Arca Noae offers a fully functional 90-day trial edition of ArcaOS 5.1. This is the closest legal answer to the "free" search.