I figure they got to be getting revenue from somewhere, but how so?

https://adblockplus.org/blog/important-changes-coming-to-the-adblock-plus-project

This is all I was able to come up with.

---
Edited by: The_Shadow, Apr 18th, 2014 @ 9:38 pm

I hope they do well.

Agreed, It's a real handy tool, and one I highly recommend for Firefox users.

From what I can tell, at least one person is working full-time on AdBlock. I'm actually not quite sure how they make money to support themselves, but it is possible to generate real income from free, open-source software:

http://programmers.stackexchange.com/questions/100685/making-money-with-open-source-as-a-developer

Of course, while this doesn't apply here, there's also a lot of people who make things for free (like the games I've made) because they enjoy it, they want to solve a problem, or they want to demonstrate their skills to companies that might actually pay them someday.

Donate money to the guy. I have twice when I feel super liberated by having a clean page.