[ska]

There is no requirement legally or from an accreditation board, sure.

However you should always do this in any context where it may come up. It's not just that this is the ethical path (it is) but failing to do so and getting caught out really undermines your credibility and thereby whatever message you were trying to get across (serious or no). There is literally no downside to doing this unless you are trying to obfuscate your connection.