My take is that it was all an unfortunate accident. FOD on runways happens. Is Continental to blame for a part coming off a plane? Well, had the Concorde accident not happened, and airport ops had done a FOD sweep, found the piece, and removed it (like all other items of FOD on a runway), no one would've said a thing. Should airport ops then be liable for not insuring a clear runway or doing enough FOD sweeps or runway inspections? Same answer of no, since airport ops can't be everywhere at once and insure every runway is clear of every bolt or piece of metal, etc, 100% of the time. Should the designers of Concorde be held liable for a design that was so easily compromised by a piece of metal on the runway? Same answer of no, because there's no way to plan for every possible type of event that could occur to an airplane and design a fix for it.
Just a bad series of events that came together at the wrong place and wrong time. A classic accident scenario. I can't find any negligence either by commission or omission here, from any side involved.