[decadentcactus]

I'd say HN is primarily read by people who already understand that it takes a while to learn these things, so it basically IS a weekend project.

If a non-technical person came along and saw it they may need clarification that no, you probably couldn't do it as well. But for most purposes it's understood that the person has been programming for longer than the weekend itself.

Also, as nickbw said it also gives an idea of the seriousness of the project rather than anything literal. A "weekend project" or so would (to me) mean something that may not last forever, but it was fun and different to try out.