WordPress MU

I want to configure it to work in subdomain.

http://mydomain.ext/ -> english Blogs Main Site
http://nl.mydomain.ext/ -> duch Blogs Main Site
http://de.mydomain.ext/ -> german Blogs Main Site
http://blog_username.mydomain.ext -> blog address

or

http://mydomain.ext/ main site
http://en.mydomain.ext/ -> english Blogs Main Site
http://nl.mydomain.ext/ -> duch Blogs Main Site
http://de.mydomain.ext/ -> german Blogs Main Site
http://blog_username.mydomain.ext -> blog address

is it posible to install wordpress mu 2 or 3 times
on sub-domain like this:

http://en.mydomain.ext/ -> english Blogs Main Site
http://nl.mydomain.ext/ -> duch Blogs Main Site
http://blog_username.mydomain.ext -> blog address

anyone ?

IMHO you need to be more clear if you want all users to be:
username.mydomain.ext
or if each country specific subdomain will also have users
en.mydomain.ext/username

The first option should be easy, but don't think the secound option will even be possible.

I think what you're ultimately going for would be next to impossible. Would be much easier to have the main domain, then send users off onto a completely seperate domain (rather than a sub) based on laguage.

You can have a normal wp or other site on the main domain then run separate mu's on each language subdomain with user blogs on each user.lang.mydomain.ext, then just formalise a single site theme across them all to tie them into one site, from the end user perspective anyways.

Would be interesting to develop interaction between the different lang mu's, maybe via a central bunch of tag clouds each in a different language, and a combined blog list, on the main domain site.

You could call it your metaMu community site. Then once that's all installed and you're insane enough you could maybe start developing a metaMu engine to unify the databases, one ring to control them all.

Good luck on your journey :)