To be fair to slack, the quote is "there's no limit to the amount of people you can add to your team". They're saying that as you team grows, there's no limit.

To be fair to slack, the quote is "there's no limit to the amount of people you can add to your team". They're saying that as you team grows, there's no limit. Not students or subscribers. Not "public channel", or "chat room", or some sort of phrase that indicates a large mass of people. If someone decided to sue them or something, I'd assume they'd have an easy defence saying they clearly meant a team of work colleagues. As many others are saying here, slack simply doesn't seem to be aimed at this use case.