I've initiated the Dutch and French forums some six years ago and I've been the Dutch moderator ever since. I passed on the moderatorship of the French forums to Claude Eichel, who passed it on recently to Romary Daval.
The Dutch forums have been doing rather well, although many of the participants are fluent in English. But also a lot of them aren't. Some things are just easier to understand or explain in your own language, and local tips and tricks would get lost in the English sections.
The French forum has done less well. Frenchmen don't even look at an international site like Apug. (The knowledge of English is rediculously low in France.) But the French section seems to regain some activity these last few months with a new moderator.
In short : Yes it's really usefull to have language sections of Apug, because not everyone speaks English fluently. There is a real need to exchange among analog photographers in your own environment. And the cross-contamination between the English and the language forums has proven very fertile.
Unfortunately, it gives some people even less need to try a bit harder. I'm sure, I could learn from topics discussed on those forums, but since I can't understand them, I'll miss that learning curve.