There are many open source contribution tasks on Sahana Eden’s website. I tested develops installation for mac, which is one of documentation tasks. The instruction is on this page: http://eden.sahanafoundation.org/wiki/Contribute/Documentation

I posted my work on the list of Sahana Eden: https://groups.google.com/forum/#!topic/sahana-eden/jCyiVNz4jhs

At first I though the open source contribution would all be codes tasks, but in fact there are many documentation tasks. Most of the documentation tasks are not difficult, but they still consume time. These kind of work are proper for beginners without much coding experience. In this specific task, I learned how to install virtual box and import virtual machine image into it, which is rewarding. Also, reading through the website of Sahana Eden gives me an impression of open source platform. I will consider continuously contributing to open source as the process is interesting as well as helping others is a good thing to do at spare time.