Dual-Licensing Situation

[Joseph Heenan]

Arnoud Engelfriet wrote:
> AR wrote:
>> Arnoud Engelfriet wrote:
>>> Well, there are no restrictions imposed upon your usage of the GPLv2
>>> software. They also don't impose conditions on your usage or distribution
>>> of the software. So what's the problem?
>>>
>>> They only say "once you start using the GPL software, we won't sell
>>> a proprietary license anymore".
>> Which is effectually adding terms to the original GPL license, because 
>> the original GPL license did not say that.
> 
> GPLv2 only forbids recipients from adding restrictions to the rights
> granted by the GPLv2. A refusal to sell a proprietary license is not
> a restriction on the rights granted by GPLv2.
> 
> "I will give any person $1000 if (s)he promises not to use any GPLv2 
> software ever."
> Oops. Did I just invalidate everyone's GPLv2 license? 

Perhaps it becomes even clearer if you consider the case of two companies:

Company A has developed and distributed some GPL software.

Company B refuses to sell you any of their proprietary software if you 
have used Company A's software.

Certainly company A is not violating the GPL in any way, and company B 
is also definitely not violating the GPL as it is not even bound by it. 
I can't see how company A & B being the same company can make it be a 
GPL violation.

(Company B's behaviour might be considered morally/ethically 
unacceptable, but they're free to choose how they run their business.)

Joseph