I'm doing this for a project I started, OpenPhoto. It's sort of like Wordpress in that anyone can download and install the software. And like Wordpress, we are trying to monetize it by providing a hosted solution.
I quickly found, for us, that hosting alone wasn't sufficient. So now we are offering complimentary solutions along side the open source product. We let you import photos from Facebook and Instagram for free. You pay to do it from Flickr.
We also automate some tasks that would otherwise be nearly impossible. Such as migrating from Deopbox to S3 (one aspect of the product is that you select where your photos are stored). This feature also let's us offer storage provided by us (required to get users up and running immediately. Then we can let hem change their mind later.
It is early in the game but people are paying. Hopefully enough users will. It becomes a win for the project and the creators since active development can continue.