There are many ways you can contribute to the Mozilla IoT community including:
Build a Web Thing - Build your own IoT device which uses the Web Thing API
Create an adapter - Create an adapter add-on to bridge an existing IoT protocol or device to the web
Hack on Project Things — Help us develop Mozilla's Web of Things implementation
All of our source code is on GitHub and you can find us in #iot on irc.mozilla.org or ask questions on Discourse.