How Do I Start Developing a Channel?

Yes, you can develop free channels. The system is very similar to the Apple App store, with Roku channels be analogous to iphone apps. A channel can be free, or cost some amount ending in 99 cents ($0.99, $1.99, $2.99, etc). The charge can be a one time, or recurring monthly or weekly. It's very easy to test/install your own channel on your unit for testing, requiring no registration with Roku whatsoever, just "side-load" the channel using the developer interface as described in the SDK documents. To have your channel accessible through the store or privately through a code (including vanity codes), you have to submit it to Roku's developer system, which DOES require registering as a developer.