The Korea times reports that starting 17March of this year South Koreans and other foreigners will be allowed to drive across the demilitarized zone in their own vehicles to Mount Geumgang.
Hyundai Asan tours said that this new "private car tour" is in response to customer complains about the limitations of group tours in chartered buses. There are some limitations, which you can read about, but for the most part this new tour seems to be "no strings attached". So, any foreigner in his or her own car can drive to Mount Geumgang for roughly 340,000 won which translates to about 350 dollars US per person.
Take a look at Mt Geumgang, it really is quite beautiful.