Officially the peak can be visited within an organised tour (trek) through the recognised guide Yan de Maroussem of Yanature. He is the only person that has permition from land owners (the most of inscribed area is private property) to do trek to almost the top of the mountain. Almost means that you can get only to so called "V" place - some 50 meters from the top. Even up to that point the trip is quite demanding (good shoes and mountain experience required).
Views from the top are really exceptional - especially those of Black River National Park. Recent price (October 2012) for 4 hours trek (usually starts at 7 a.m.) was around 40 Euro. You will feel every single euro while climbing the mountain.