It’s not the only way nor even the best way. A lot has changed since I started writing these and the UI is being completely rewritten which is largely why I stopped writing this series. It will be picked back up again soon and it will make it into the docs. There is already a really good start to a beginner;s tutorial you can find here.
A whole lot has changed with the JavaScript libraries too, which you can find out more about at Helper Libraries for openHAB Scripted Automation — openHAB Helper Libraries documentation about how to install and use them.
But if you are using anything but Rules DSL in OH 2.X you are using the NGRE. In OH 3, it’ll be just called the Rule Engine and it will also run Rules DSL.