Python style: exceptions vs. sys.exit()

Steven D'Aprano steven at
Fri Oct 3 11:04:44 CEST 2008

On Fri, 03 Oct 2008 17:09:07 +1200, greg wrote:

> Lawrence D'Oliveiro wrote:
>> In message <00f15d41$0$20617$c3e8da3 at>, Steven
>> D'Aprano wrote:
>> > (2) Even when the source is available, it is sometimes a legal trap
>> > to read it with respect to patents and copyright.
>> That's not how patents work.
> I don't think that's how copyrights work either. As far as I know,
> whether something is deemed a derivative work is judged on the basis of
> how similar it is to another work, not whether its author had knowledge
> of the other work. As long as you express an idea in an original way, it
> shouldn't matter where you got the idea from.

That is absolutely not the case with patents. It is *supposed* to be the 
case with copyrights, but in practice the courts are interpreting 
"derivative work" more and more broadly these days.

As for Microsoft Shared Source licences, there are two which are approved 
by the FSF, but the others are a whole different story.

You will note that both the GNU project and the Mono project warn against 
reading proprietary source code before contributing. Mono even goes so 
far as to say that if you have read the source code to .NET, they cannot 
accept your contributions:

    If you have looked at Microsoft's implementation of .NET or
    their shared source code, you will not be able to contribute 
    to Mono. 
    In general, be careful when you are implementing free software 
    and you have access to proprietary code. We need to make sure 
    that we are not using someone else's copyrighted code 


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