I have no idea about Zulip, it was harder to setup under pressure than Mattermost was.
I am sure that being forced to spend time on this steals time from more interesting projects.
How long have they had the bill mentioned in the top comment on this post? At the very least it's 3 weeks, and the comment suggests it is months.
Both times I’ve paid the new price for 1 year and cancelled. Both times our sales rep was surprised the next year when we didn’t renew.
I'm not denying that what you describe happens, but in this case - ignoring the warning signs, letting the issue crash into a wall and then complaining online about it doesn't help anyone.
There's a couple of interpretations here.
1. The sales rep really thought they would be able to retain good pricing for them and it fell through, and at the last minute hackclub was blindsided by their inability to retain the pricing.
2. The sales rep thought that hackclub was likely to jump ship if they had time to plan based on the new pricing, and lied to them about the possibility of retaining pricing. And thought that by doing so they could force at least one year of higher cost.
3. Hack Club is misrepresenting their communications with Slack to drum up public approval.
My guess is that option 1 is the most likely, and the optimism of the sales rep ended up being a net negative, and human nature being what it is, Hack Club thought things would work out, and everyone is already busy so why borrow trouble.
As for complaining online, sadly it seems that bad press is the only lever that most people have as a forcing factor for companies these days. I honestly only had a Twitter account for a long time, just so I could complain about companies in public to get them to do the right thing, so unfortunately complaining online does actually help.
I'm not defending Slack here, but allowing this to hit the wall and then raising a stink online does everyone a disservice.
Edit: by "you", I mean "the organisation of Skyfall". It's already pretty clear from the number of people chiming in on behalf of the company that this problem has been handed out piecemeal.
From the top comment, if Hack Club was told to ignore it and not pay, I don't feel they are to blame.
I disagree; this is the best time to unlearn "companies selling proprietary software are our friends"
Arguably it's a more valuable lesson than any technical lesson: ignoring existing open source projects in favour of proprietary stuff should hurt.
The more it hurts the better the lesson sticks.