They are profiting out of mongodb, they are getting people to invest lots of time, trust, and money in their product.

The author has a strong point that quality of the development process for mongodb must not be good if a bug like this one gets into production, when it could be avoided using automated tools. This won't be such a fault for a random open source project, but if you are making a business out of it, and you are encouraging others to base use it as a key part of their business it do is a great problem.