First of all, i think we all are right. I don't want to get in a tug of war game.

not everyone speaks (writes in this case) english
Totally true. I rely a lot on the 'check spelling' future in firefox. Than won't do grammar though.
technical terms/measures/verbs/...
Personally i get most of the technical terms i use from datasheets or wikipedia. As i search for those in google not set for dutch language i get mostly english results.
In a broader sense; When i search for information on the internet i think it is limiting if i search in dutch only. Matter of how many people speak dutch vs other languages. With that in mind i should learn mandarin chinese, hindi or at least spanish.

So it always helps if a user can ask questions in their mother/native language.
I will help, yes. With the disadvantage of 'hiding' information for non-dutch members.
I would have thought that english would not be a problem for most dutch people. Especially the techies.
Another 2 cents.
Jeroen