We've put in a possibility to donate for server upkeep on the website now: http://www.nwn2planescape.com/donate.html
Don't worry though, the server is financially secured, so only donate if you feel like giving a contribution to the running costs.
We're not going to nag about donations at any time, this is only a "for your information" announcement, and we will unlikely post any new announcements about it later.