I don't know much about the codes you've mentioned, but I don't see any downside to having one at this point. So I will support it if people feel it is valuable.
I don't think the forum guidelines apply here, so having clarity relating to coder/developer behaviour is a positive IMO.
I think it has been helpful to have guidelines on the forum because even if some disregard them: 1) it reassures people about what they can expect from the mods, and others, and helps them understand what is expected of them. 2) it encourages people to report things that go against the guidelines. 3) it's useful to be able to refer to them as a moderator, both to know what is OK and what's not, and to refer people to when they go too far. Without explicit guidelines transgressors can more easily take things personally, which seems to be a common thing among those who behave badly towards others online. When someone takes things personally it makes things very much harder to manage as we've seen.
I think roughly the same applies to the developer community, although probably to a lesser extent than with a community forum.