Problem is the military drive. I can imagine one or two being converted to civilian drives but more likely if any did make it out of military hands their drive systems were decommissioned and a stationary power plant installed. I can imagine an immobile Oberth serving as a private research station and sensor platform.
An Oberth is many decades out of date and, at D1, presumably has a slower and less advanced drive than is typical of the nicer modern private craft. What's the issue? I really doubt that civilian craft are all fusion powered if that's what you are suggesting, and in any case any starship at all in the wrong hands without anyone else on hands who can stop it is by default a potential weapon of mass destruction, so anyone allowed to operate a starship would have to be regarded as somewhat trustworthy.