Oberon

Oberon is a structured object oriented and procedural language in the Algol family that was introduced by Niklaus Wirth in 1988 alongside an operating system with the same name. It was based on his earlier Modula 2 language but adds limited object-orientation but at the same time removes a lot of the features in order to simplify the language and compiler. Oberon-2 is an extension of Oberon developed in 1992 by Hanspeter Mössenböck that adds stronger object-orientation and brings back a couple of features from Modula 2.

Note that with the exception of the Oberon compilers developed by Hr. Wirth himself that in general only support the original Oberon, most developers support both languages without explicitly mentioning it, this is because Oberon-2 is purely and addition to Oberon and therefore you can program in the earlier variation without any problems. But the literature does frequently not differentiate correctly between the two.

There are descendant languages that some classify as Oberon and others as members of the Oberon family, we include the few implementations that actually run under OS/2 in some form here just to simplify things, it is not a taxidermy issue. Active Oberon is a variant of either Oberon or Oberon-2 that has explicit support for programming multi core processors, Oberon/0 is a simplified version of the language intended to be used in teaching compiler construction, it is therefore as much a descendant of PL/0 (simplified Pascal) as of Oberon proper and you are not meant to download a copy, but rather make one yourself.

Oberon/L is now called Component Pascal is a variant designed specifically to allow development of software components, there is no native OS/2 implementation but a Java implementation exists and Blackbox Oberon runs fine under Odin, Blackbox Oberon used to be called Oberon/F BTW. Zonnon is a descendant of Active Oberon that adds safety features and a stronger object system. Oberon07 is simply a name for the latest version of the Oberon standard and does not differ too much from the original, the last update to the Oberon 07 standard was in the summer of 2014.

A list of OS/2 implementations of Oberon

Canterbury Modula 2 & Oberon-2 - Discontinued
ETH Oberon System - Discontinued. Note that this is not just the compiler but the entire Oberon OS as a layer on top of OS/2 or eCS.
Gardens Point Oberon-2 Was available in both Commercial and Open Source variants - Discontinued.
IBM Oberon-2 - Internal use only - Was talked about as a EWS release but appears never to have seen the light of day.
XDS-x86 Modula 2 - Discontinued

A list of DOS implementations of Oberon

Gardens Point Oberon-2 Was available in both Commercial and Open Source variants - Discontinued.
XDS-x86 Modula 2 - Discontinued

A list of Oberon implementations that run under WinOS/2

Programmers Open Workbench - Aka POW! 16 - Open source - Discontinued

A list of Oberon implementations that run under Java

Canterbury Oberon-2 for Java - Discontinued
JOB - Open source - Discontinued

A list of Oberon implementations in JavaScript

OberonScript - Can be run inside a web browser or by using the JavaScript Desktop Enabler.
Microsoft Oberon Script - Older version of the above, code appears to have gone missing.