[whpalmer4]

To expand upon pvonk's answer a bit:

OF is not designed to be used as groupware. That doesn't mean you can't do it, but there are some cases that can bite you if you aren't careful. Essentially, OmniFocus assumes that only one person at a time will be editing any given item (you won't be making simultaneous changes on two different Macs, or on a Mac and an iPhone, etc.) If that assumption is violated, the earlier change will be silently discarded. What this means is if you and your assistant happen to edit the same action and then sync, one of those changes will vanish. That could be pretty serious if you were making some notes, and the assistant was updating the due date; if your change came second, you'd get your notes, but no one would notice that the due date change didn't stick. I believe that there are some more subtle cases as well where you might lose changes to the ordering of actions, etc.

So, if you can make sure that neither of you is making changes at the same time to the same things, it should work. That may not be very practical, or it may be completely reasonable.

From a licensing standpoint, you'll need to own two copies of OmniFocus to be in compliance, as the license allows for one person to use it on a number of computers, or a number of people to use it on the same computer. You would presumably have two people and two computers. To clarify, I'm speaking of the license for a copy bought directly from Omni; if you buy through the App Store the licensing is different, but I only know that it is different, not how it differs.