A conversation that seems to have happened quite a few times for me in the past 6 months or so is why I think Open Source is important. You may have read something like this before. I feel like I should write it up so I can remember and others can understand.
I participate in the Fedora project and am very excited to be a part of it. This is my volunteer project. This also happens to benefit me professionally since Fedora is the upstream distribution on which Red Hat bases RHEL. A larger global reason for my participation in the project is also that I believe that Open Source Software/Ideas/Projects are something that benefit everyone.
Personally, that's a huge motivation. Teaching and learning are the two most important activities that I think we, humans, can participate in. I personally feel that once you stop learning, there isn't much point in going on. Thank you Mom and Dad for instilling in me this incredible desire to want to know how the world works.
I've been a teacher pretty much since I was in High School - I tutored 5th and 6th graders in math, tutored fellow college students in math at the math center in college, trained co-workers when I started working professionally on the technologies and concepts that I knew, etc., and, more recently, have become a professional Instructor. Being a teacher/tutor/mentor has enabled me to accelerate my learning and has really kept me interested in the latest and greatest things that humanity has come up with - technological, scientific, medical, and concepts.
I have found that Open Source projects are one of the most rewarding ways in which to learn (receive), teach (give) and participate (fulling sense of purpose). I love Open Source.