There are many other alternatives to do good in Borneo or for Borneo or for orangutans.
If you want to help a charity, why not give money to the charity directly. If you want to visit them you may be able to do so at their visitor centre, pay the entrance fee and if you wish make a donation.
Many of the so called volunteering projects are low skilled labour projects. Some of the regions where these volunteering projects take place may have high unemployment. It may be more beneficial for the local economy to employ a local trades person, who does the job.
Will your volunteering trip really make a difference? Probably not.
If you are a doctor or another skilled professional, you may be able to make a real difference. If you do not have any profession, you probably will not make any difference.
It may just be a feel good experience for yourself and new content for your social media.
Most volunteering travel is offered by travel companies, who have an arrangement with a local organisation or company, where volunteers work on a project.
It has not been unheard of that so called volunteers do a project that a previous volunteer group has already done. Volunteering travel is a travel tour like any other.
The costs can be a high as £100 per day for basic accommodation and food, which may be worth as little as £15 -20 per day together with a full day of work doing non skilled labour. Very little of your volunteering travel fees may go to any charity.