Accidental is not a valid reason, same as ignorance. Otherwise everyone could just say they accidentally committed a crime. That necklace accidentally fell in my purse, I was accidentally speeding, etc.

> Accidental is not a valid reason, same as ignorance

While this happens to be true in this specific case, as a general statement, it's misleading. It is true for copyright infringement because that is a strict liability tort, which means it doesn't require any particular state of mind ('mens rea'[0]).

Not all torts, and not all crimes, are strict liability. In your examples, if a necklace accidentally falls into your purse, that is not theft (in English law, anyway), as theft requires intent to deprive the owner of the thing[1]. Though once you notice it, if you decide not to return it, at that point it will become theft. Speeding, on the other hand, is strict liability (again: in English law, I don't know about US), as are most minor regulatory-type offences where it'd be difficult and impractical to prove intent.

(Also note: tort != crime. Copyright infringement can in some circumstances be a crime, but this is a lawsuit: the company is suing the Navy; the Navy isn't being prosecuted).

[0] https://en.wikipedia.org/wiki/Mens_rea

[1] http://www.legislation.gov.uk/ukpga/1968/60

NB: IANAL (did law, but ended up going into software dev instead)

That doesn't change if they intended to do it or not, its a clear copyright violation never the less (given the facts in the article are avcurate). I'm curious about what they actually intended to do.

The type of copyright violation matters. Copies in the dusty recesses of a drive image are a lot more minor than it actually being used by a million people.