The passage in Numbers 15 would seem to refer to something that was not required to be done on the Sabbath - after all, the man had had 6 days to collect enough (rather like the people were told not to collect excess manna - but only enough for that day - except on the 6th day, when a double collection would not go bad).  As such, it would appear that the man concerned was intentionally breaking the interpretation that had been laid down by the leaders of the people.

Martin, I've reposted the section that you seem to have ignored.  The death sentence is, in my view, a completely different issue.  Yes, it appears barbaric to urbanised Western thinking, but it isn't unusual in nomadic societies even today.