I'm still really hoping for this too. I think it is very much GTD consistent.
I have written several articles for GTDtimes and have never come across anything in my reading of official GTD materials that would suggest that you can't include something in more than one context. If the action can be completed at more than one location or more than one context in a paper based model you would write in on both context cards (pages, etc). With digitally based GTD this seems to be a very natural extension that allows the app to get one more sort of detail out of your mind and into your system so your system, OF, in this case can remind you of when you're in a context where you can complete a next action.
I would think the solution could be as simple as when you select a context on the drop down that it simply puts a check mark by the context you want from the list. You could drop down again to add another context.
I really enjoy this software. I think this would be a big bonus that would make lots of OF users happy.
I should have posted
this on this thread.