"If Mozilla permit the sale of copied versions of its software, it
makes it virtually impossible for us, [UK trading standards] from a
practical point of view, to enforce UK anti-piracy legislation, as it
is difficult for us to give general advice to businesses over what
is/is not permitted."
Surely it can't be that difficult. The 'general advice' should be to comply with the terms of the licence for the particular software involved. The fact there is more than one type of software licence shouldn't be that hard to understand.