There are many reviewers and pundits who have discussed the recent Supreme Court case of Microsoft v. ATT, which dealt with a patent that Microsoft admitted to contributory infringement. This meant that Microsoft’s software enabled someone else to infringe, but that Microsoft itself did not directly infringe. The question was whether or not Microsoft was to be liable for infringement outside the US because Microsoft sent master copies of infringing software overseas for copying and foreign distribution and whether that action amounted to infringement.
The court decided that Microsoft was not liable because Microsoft did not export the copies of Windows installed on the foreign made computers. Instead, Microsoft supplied a master from which copies were made.
This is a very, very fine distinction.