How are developers being treated "unfairly"?
The work is being released as open source. The developer has already chosen to give up the rights to any profit they might obtain from commercial use of the software. If that isn't desired there's any number of alternative licensing schemes that would require compensation for commercial use.
They aren't being forced to work on the software. They can contribute as much or as little to it as they like.
So what would make it fair, exactly?
https://www.google.com/search?q=define+exploitation
Exploitation: the action or fact of treating someone unfairly in order to benefit from their work.
It comes down to whether you think it's fair or not, which is a question of morality.