It did helped me a lot. I get to understand the nuances of grunt, jasmine, mocha a lot from the author. He did teach me a lot about JS programming and I get to see how hard it is to contribute keeping your day job on the boil. Overall, it is a nice experience. Trust me, I still have couple of Issues/PRs pending and I'm yet to find time to do that!
Mayank Chandola
Yes. Open source projects and contributions do help you a lot in both learning and also as a developer or freelancer. I myself have learned a lot of new things after I started contributing to open source.