[Maximilian]

Originally Posted by steve

Thanks for all of your help with this. Unfortunately:

1) Omnifocus can't import an Omnifocus file. I will report a bug.
2) Even though I am focused on a project, all of my projects are exported.

Unless someone else gets it to work or has another idea, I would agree with whpalmer4's original assessment:

Seems you are right OF exports ALWAYS your whole database you do not want necessarily to share. Two ways dealing with this are
a) opening the exported file (I used OF archive format) by double-click - which opens it into a new window and there deleting all unwanted folders/projects. Then closing/saving the edited version ready for sharing; or
b) sending the whole thing and leaving it up to the receiver to open your complete OF database and dragging from there the only relevant project folder into their (receiver's) OF main window. And then deleting what they received from you. But for that you have to trust them to deal with the overload - hence I prefer a).

Nevertheless, exporting only selected projects/folders I would say is a must for OF!
Good luck.