[userbinator]

Also how was the c64 not a 'closed proprietary system'?

It's been completely reverse-engineered, emulated, and documented, a lot more than can be said of the SoC in the RPi. Maybe in 30 years the same will happen to the latter, but I'm not too optimistic about that.

[nickpsecurity]

That means it was a closed, proprietary system that was reverse engineered & emulated. Different from an open system that doesn't require that. Also more efficient in hardware if any clones port original design.

[pareidolia]

You are incorrect. The documentation supplied with the C64 detailed schematics and ROM routines:

C64: http://www.classiccmp.org/cini/pdf/Commodore/C64%20Programme...

C128: http://www.pagetable.com/docs/Commodore%20128%20Programmer's...

[nickpsecurity]

Did they give you copyright and patent licenses allowing you to do whatever you wanted with their tech? Or did a cloner have to hope the company would take no legal action?

Because that's still not equal to an open-source design where the licensing eliminates such risks.