[Ken Case]

There are a lot of features in OmniFocus which allow methodologies that don't fit within traditional GTD.

For example, with the Flagged and Due Soon filters, you can sort your objects into Stephen Covey's four quadrants (Important = Flagged, Due Soon = Urgent), and using Perspectives you can give each of those quadrants a button on your toolbar (each with its own representative custom icon).

The notion of focus (i.e., focusing on your Work or Personal folder—or even a single project—and ignoring all the other actions that you could be doing in your current context) is also very different from the traditional GTD workflow (which suggests you look at everything available in your current context when deciding which to do next).

GTD suggests you only use due dates when you have a hard date that you absolutely cannot miss without making the action irrelevant, but many people using OmniFocus use due dates exclusively to plan and schedule their work load, ignoring the contexts altogether.

Some people implement more granular levels of priority by using the context list to hold priority levels (e.g., contexts like URGENT, High, Medium, Low) and ignore the way GTDers might use those contexts.

OmniFocus supports planning out a project in detail (with parallel and sequential actions), while GTD suggests you just figure out the very next action you need to do to move a project and then go to work on that.

So yes, we were inspired by GTD and we think OmniFocus does a great job of supporting GTD's patterns, but those are certainly not the only source of inspiration and those are not the only patterns it supports.