I just saw a plane overhead that was flying unusual low and it turns out it was a 737 MAX 8 that left from the Boeing factory in Renton.
Are planes that are not yet operated by airlines exempt from being grounded?
It looks like the link is no longer active but in addition to Anilv's answer the EASA order also allows for ferry flight to have the aircraft fixed.
From the effective date and time of this AD, do not operate the aeroplane, except that a single non-commercial ferry flight (up to three flight cycles) may be accomplished to return the aeroplane to a location where the expected corrective action(s) can be accomplished.
Emergency order issued by the FAA allows for special flights including production flights testing, ferry etc. The order is available on the FAA website.