Glad you are asking this question... but... I think it would be wise to ask what a respondent's motivation for building/maintaining their open source project really is. Often times, monetization is really low on the priority list.
For me it is split. I develop open source licensed software at work and my employer tries to make revenue. Privately I do stuff for fun and don't want the responsibilities of having "customers." If people use it for free and make money, so be it, but I have the liberty to stop/pause working on it.
That can happen, but sometimes monetization isn't the answer. Getting more contributors is. As the song goes, "Can't buy me love..."