To fork or not to fork?
When you are creating a new extension for Joomla!, should you start from scratch, or fork another similar extension, or use an extension building component? This book is going to cover creating an extension from scratch, so you can learn all the basics. Once you know these, you may wish to fork the extensions we make together or even fork one of your own extensions to save you a lot of time if you need to make something similar.
There are several extension building components that will prompt you for a bit of information, then create a basic component, plugin, or module based on the information you provide. EasyCreator is one such extension that I have used in the past, but you still need to know the basics to be able to modify this automatically generated code to suit your needs. If you want to know more about these types of extension building components, you can refer to the development category within the miscellaneous category on the JED. The JED listing for EasyCreator can be found at http://extensions.joomla.org/extensions/miscellaneous/development/5908.
With regards to forking someone else's extensions, you probably should first approach the developer and discuss your ideas and see if there is an opportunity to work together to make the original extension even better. If the developer has lost interest in further developing the extension or if you have a completely different vision that will take the software down an entirely different path, then there may be an opportunity to fork the extension rather than starting over from scratch.