This is going to get lawerly. Apologies in advance.
There are three issues with those two sentences.
One is that it is Wordpress' view and not determinative of how the GPL will actually be interpreted (it is basically a guess on their part).
The second is that it mixes two uses of the word 'distribute'. The first sentence concerns the scope of the GPL. Does it apply only to distributed derivatives, or does it also apply to non-distributed derivatives? The second sentence concerns the questions of what obligations the GPL places on derivative works to which it applies. If you read it a couple of times, you may notice there is a contradiction on the face of the meaning of those two sentences. If the GPL does not apply to non-distributed works as the first sentence claims, then how can it be determinative on the requirements placed on non-distributed works as the second sentence implies? This prima facie contradiction can be resolved, but it points to the fact that the slippage in usage is a bit sloppy.
The third is it that is relatively easy to sow doubts about what is painted as a relatively categorical interpretation of the GPL. This is exactly what lawyers will do in a relevant case. This is how it will be done.
Take this phrase used throughout clauses 1 to 3 of the GPL.
copy and distribute
Now, on first reading you may have thought that means that it applies to situations in which people both copy and distribute a work. On this reading 'distribution' is always a necessary part of use to which the GPL applies. There is another reading of this phrase which renders 'copy' and 'distribute' as divisible elements. This would mean the GPL applies to either copying or distributing a work. This interpretation may seem implausible to you as you feel that normally when you see two nouns joined by 'and' you read them conjunctively.
However, lets look at other uses of the words 'copy' and 'distribute' are used in the GPL (which is what a court will do when trying to resolve grammatical ambiguities).
Activities other than copying, distribution and modification are not covered by this License; they are outside its scope.
This sentence seems to use the verbs disjunctively. And in fact is directly referring to the scope of the GPL.
You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License.
Same as above.
It would be quite easy to make a case of contractual interpretation that the GPL applies to non-distributed derivatives.
Now, I'm not saying that that is how the GPL will be interpreted. I would reiterate what I said in response to Jeff's post that, this is really speculation. And perhaps best left to lawyers to speculate over, rather than worry too much about at this stage.
But, that said, if I were thinking of starting a business or a career in work based on derivative works of an open source project like Discourse or Wordpress which uses GPL v2 (as I am), I would want to understand that there is a legal risk involved given:
- The terms of the GPL.
- The lack of legal precedent concerning the construction of the GPL.
- The general uncertainty and ambiguity around this area of law.
Regardless of how well established we think of Wordpress and how large it looms in our minds, a judge or the legal system (and keep in mind we're talking about all legal systems, not just the US legal system) generally, will largely not care. They will look at the terms of the license.
Disclaimer: none of this post or previous posts constitutes legal advice.