[BruceM]

I've occasionally wanted to run System3 again. I wonder what it would take (for OS X)...

[pjmlp]

You can run it as part of AoS, as System 3 Kernel module is remapped to Active Oberon Kernel module.

http://www.ocp.inf.ethz.ch/wiki/Documentation/Front

But Active Oberon fails to run on modern hardware, the best you can do is a VM, and even then builds tend to be scarce.

http://www.ocp.inf.ethz.ch/forum/index.php/topic,692.0.html