Legal/Permission Question

[Walter Bright]

Gregor Richards wrote:
> Dan wrote:
>> Hey Walter/anyone?
>>
>> Considering that my Walnut 2.x engine performs much the same 
>> functionality as DMDScript, but that Walnut 2.x is written 
>> significantly differently on a structural level...
>>
>> DMDScript is a GPL v1 engine, and Walnut 2.x is a new BSD engine.
>>
>> When I fill in the function stubs for, for example, 
>> Number_prototype_toFixed, am I allowed to examine Walter's DMDScript 
>> source code, write something similar (but obviously not the same) and 
>> still call it new BSD?
>>
>> What requirements are there to do such a thing?
> 
> This is one of many distinctions between copyright and patent.
> 
> Copyright covers the RIGHT to COPY. NOTHING ELSE. Unless you signed a 
> license or contract specifying that you can't use it as a reference, you 
> can.

I believe this is incorrect. Copyrights also cover 'derivative works'. 
See http://en.wikipedia.org/wiki/Derivative_work