Ok, checking out Meecast a little bit, it seems they are using a couple of different sources: openweathermap.org (which may be usable for a community as small as Maemo now is), foreca.com (which doesn't seem to have an official free feed), and yr.no (a Russian-area site also used by OMWeather).

I think an app based mostly on openweathermap.org is probably the most feasible choice for an open source app going forward; but still, once that limit is hit, service for all users will be disrupted until it gets restored...