One of the foundations of open source is the idea that developers should not earn money by selling finished products, but by using services (consulting, implementation, maintenance).
The new project sourceforge.net, called the original
Marketplace :), just provides such an opportunity.
Now, for example, the developer of any program distributed, of course, on the terms of open source, will be able to offer interested users its already non-free technical support. Sourceforge.net itself expects to earn commissions from payments made.