Yeah that should work.
Is it working?
You have to rename the documentname also, it has to be bbpress-nl_NL.mo
What language is set in your WordPress installation (your dashboard, is is in english or dutch?)
If it is dutch it should work immidiatly, otherwise you have to make a small change in your wp-config file.
Change this line in wp congif:
define ('WPLANG', '');
to:
define (‘WPLANG’, ‘nl_NL’);
That was stupid.. thanks, 2.3 is working 🙂