I got the hotjar beta email earlier today actually
I actually had received the email, I just, missed it.
I ran it previously for a week or two, and found it was hammering page load times, so I removed it. They sent me an automated email along the lines of "we've not seen you for a while", which I replied to with "it was hammering page loads, so I binned it",
I got a personalised reply back from the head of engineering yesterday asking to help me look into it, gave me 2 years free and explained that they'd recently updated their hotjar scripts to use websockets rather than, something else. So I'm now utilising my free 2 year package with the ability to record what people do on my site.
I've also linked them to NodeBB if they need a support forum.