It seems no one gets hindered to post in English, so it's up to the users (which is a good thing, imho).
That said:
I for one would appreciate more posts in English. If i do computing, i do it in English (mainly to learn English, btw). I only check the English forum, and it rather seems silent.
It also seems to make sense: the de facto standard to communicate international is English. While there are lots of Germans and a lot of people in Europe who speak German, a lot do not. English, otoh, is spoken by most people, it seems (at least the younger generations).
I am not really an active member of the sidux/aptosid/siduction community, so the above is just a side note (let's say from a stranger). One of the reasons might be the amount of German communication (the other one being the strict moderation in the past, at the sidux forum).