I have read that for open source software developers, 3 common ways to make money are hosting, consulting, and support. I understand support and consulting but what is hosting?
When I read 'hosting' I think of a hosting site like GoDaddy, but clearly that is not being mentioned here.
Hosting - Basically for SaaS solutions, As Adrian said like Wordpress, or Hadoop Based services. Also hosted software provides Service Level Agreements
Also don't forget extended features, look at Red Hat Linux, MySQL Enterprise, and loads of others
Another approach may be that: you host the project/source code/... that if for free but it generates traffic to your site. The developer can thus earn money by ads on the website or perhaps by affiliate programs for other paid products that he recommends.
But of course, the meaning of the "hosting" should be explained by the author of the thought/article you have read. Because there are many possible interpretations of such a statement.