1. The organisation is run by a BoD of unpaid volunteers.
1. It does not matter… BOD can be a dues paying or not paying BOD… no difference legally

I know that, I meant it might make a difference to the answers you receive on the forum

2. Some sellers are members of the organisation.
2. Yes… we have a 501c3 that has a membership program… unrelated to BOD

3. Some sellers are NOT members of the organisation.
3. Why would public use effect anything? it is a public forum.

4. Some sellers are those in 1. above while not acting in their BoD roles.
4. If you are a board member of a 501c3, you should not profit "personally" from the activities of the
not for profits's work. In this case… members of the BOD should probably not sell their own
chips for personal gain on the club's website. BOD serves to help further the mission not to make a profit from it.

How can you say the club's website would be part of the activities of the not for profit's work? You've just agreed it is a public forum in 3. above. Therefore no reason why a BOD member can't sell there also.