You don't have to apply for a work or residence permit, which means that you can stay in the country indefinitely. If you're from the EEA you have to exit Norway every 3 months, unless you qualify for a work and residence permit, basically, you have to have a job.
Is the 3-month thing actually enforced in Norway on those who do not cause a nuisance or seek benefits? Not only is it rarely enforced in EU countries, but I vaguely recall hearing that there have been court judgements in some country or another that EU/EEA citizens who overstay there cannot be forced to leave.