The Borneo Orangutan Survival (BOS) Foundation is an Indonesian non-profit NGO founded by Dr Willie Smits in 1991 and dedicated to the conservation of the endangered Bornean orangutan and its habitat through the involvement of local people. It is audited by a multinational auditor company and operates under the formal agreement with the Indonesian Ministry of Forest to conserve and rehabilitate orangutans. BOS manages orangutan rescue, rehabilitation and re-introduction programmes in East and Central Kalimantan. With more than 500 orangutans (per December 2018) in its care and employing between six hundred and a thousand people at a hundred sites BOS is the biggest primate conservation NGO worldwide. Nyaru Menteng and Samboja Lestari are the BOS sites that have received most extensive media coverage. Nyaru Menteng, founded by Lone Drøscher Nielsen, has been the subject of a number of TV series, including Orangutan Diary and Orangutan Island.
Although they seem like the provide a great trade-free service, the following is worth mentioning:
“To finance the nature reserve, BOS created a system of “land-purchasing”, a “Create Rainforest” initiative where donors can symbolically adopt square metres of rainforest and are able to view and follow the progress of their “purchase” in the project area with Google Earth satellite images from 2002 and 2007 with additional information overlaid.” https://en.wikipedia.org/wiki/Borneo_Orangutan_Survival