Netcentrics' GTDOA still works on Outlook 2016! However, it will not work on future versions
WHile I have not read the "GTD & Outlook Setup Guide", I created work-arounds for virtually all of the GTDOA functioanlity as well better task views.
"You just won't have the cool features that Netcentrics adds like linking and seeing actions by project." - kelstarrising
My workaround for this is to create a seperate Task folder for each project. (GTDOA does this for the someday list.) Outlook's To-Do view is a composite of all of the tasks in all of your Task folders so you can pull a view of your GTD actions.
I am undecided as to how to create the GTD project list in Outlook. I have created special 'header tasks' that I stored in each of the Task folders by project. I currently store these header tasks in the main Outlook Task folder. Either way, they are read by an Outlook Task view that I can flip to whenever I want to see my GTD projects list.
I do not see a point to any of the current third party Outlook add-ins because;
1. Outlook in its native form has functiolaity robust enought to be a platform for all of GTD
2. All of these 3rd party add-ins are subscription based - you have to pay every month to use it.
3. Many corporate IT departments do not allow 3rd party-aps