The easiest thing to do here is probably going to be to take advantage of the "Publish Due reminders as a calendar" feature that all three editions of OmniFocus offer in the Sync settings.
That feature will add reminders of all your deadlines for the next two weeks to a calendar file, then help you subscribe BusyCal to that calendar. (The "Subscribe in iCal" button works just fine with BusyCal, too.)
From then on, every time you sync OmniFocus, that calendar file will be updated; BusyCal will notice the changes and show them on your calendar. You can enable a similar setting on your iPad and iPhone, as well so they can also update the calendar file and show the reminders in the built-in Calendar app.
Since you're already syncing, all you
should need to do is open nte Sync preferences in OmniFocus for Mac, then check the appropriate box and press the "Subscribe" button and possibly enter your login info for the server you use to sync. (The process is very similar in the iOS apps.)
If that doesn't work or anything unexpected happens, though, just email our
support ninjas and we'll be happy to help get this set up!