Task List for Multiple Users
 

Is there a way for multiple users to access one OmniFocus file AND to add tasks, mark them completed, and maintain a log of completed tasks for all to view?

Yes and not yet.

Yes, multiple people could access one file (just set the sync settings the same on each person's computer) and make all the same edits a single user could. And you could set up a perspective for completed items, possibly sorted by completion date.

[b]However[/b], this does open up a risk of data loss. If 2 people edit the same item at about the same time, one person's changes could get lost. For example, I change the due date of the action, then you add a note, then we both sync. Your note will get saved and my due date will be lost.

So, really, the answer is "not yet". We want to add some collaboration features to OmniFocus, but have not yet done so.

And lest you're thinking "oh, that's okay, we can just add the change again" let me caution you that you won't get any sort of notification that one of your changes has been lost! Kind of a bummer when the change that gets lost is the new due date, and you only find out thanks to the customer's irate phone call...

OmniFocus with a single user avoids this problem because most people don't have enough hands to make changes on two devices at once :-)

I agree with whpalmer4. I should have been stronger in emphasizing that we really do not recommend you have multiple people working from the same database. It happens to sort of work, but that's not what OmniFocus was designed for.

You might also take a look at OmniPlan, which IS already designed for multiple users, change tracking, and conflict resolution.