How does this website www.crazyengineers.com earn money? And how many engineers have signed up during that referral contest?

CrazyEngineers primarily makes money through online advertisements displayed on the site. As of now; we've disabled the advertisements are are trying out a new business model in the form of products and services. Our vision is to build CE into a platform where every engineer gets any help they need. 

The version that you currently see on the site is the upgraded version (launched on May 18, 2018). Until then we were primarily an online discussion forum. 

The Super Referral contest was our 'pilot' project done at a small scale to evaluate an upcoming initiative. We got a a little over 800 sign-ups through the contest.

If you have the time: You could read -

1. <a href="https://www.crazyengineers.com/threads/the-story-of-crazyengineers-how-ce-came-to-life.38227">The Story Of CrazyEngineers - How CE Came To Life</a>

2. <a href="https://yourstory.com/2009/01/kaustubh-katdare-creator-crazyengineers" target="_blank" rel="noopener noreferrer">Kaustubh Katdare, Creator , CrazyEngineers</a>