I am using RequireJS and need to initialize something on DOM ready. Now, RequireJS provides the domReady plugin, but we already have jQuery\'s $(document).ready()
Answering your bullets in order of appearance:
When it comes down to it, you are overthinking this. It's a mechanism to execute javascript on domReady. If you didn't have jQuery I would advocate the domReady plugin. Since you have jQuery then don't load more scripts to do something that is already available.
Clarity Update
The domReady plugin collects functions to call when the document is 'ready'. If it is already loaded then they execute immediately.
JQuery collects functions and binds a deferred object to the dom being 'ready'. When the dom is ready the deferred object will be resolved and the functions will fire. If the dom is already 'ready' then the deferred will already be resolved so the function will execute immediately.
This means that effectively they do exactly the same thing.