Your passport will be clearly stamped "Permitted to remain on condition that the holder does not enter into employment paid or unpaid and does not engage in any business or profession without the consent of the director of immigration..."
Doing volunteer work for an organization that benefits the community is a bit different than trying to get a free stay for doing work that could be done by a national or resident.
I love all the posts from people who get upset about Belize immigration laws but don't bother to think about the laws of their own country.
Many Belizeans would love to be able to run up to the States or Canada and grab a job in the area of their choice but they can't because of immigration laws. Why should this country be looked down upon for its right to enforce it's own immigration laws.
I don't know if your last comment was directed to me. I don't look down at Belize Immigration laws. But I was looking at travelling to many hot subtropical to tropical counties that had work exchange program that didn't require any permits so its an aggreement with the participate and hostel. And its not a program recognize by immigration like many exchange programs geared to having many people from other countries to come to countries like Belize for a learning experience