The post makes it sound like it's a copy of https://github.com/cjb/serverless-webrtc uploaded to IPFS; examining the code [1] shows that '23.21.150.121' is hardcoded for STUN.

This was seemingly set up by Wesley Dawson [2] at Mozilla in 2013, at which point it was an EC2 machine in AWS us-east-1. It subsequently made it into various gists and projects as a public STUN server.

Later in 2013 Mozilla changed over to using a hostname in Firefox instead [3], and much later Firefox 41 removed [4] Mozilla's STUN servers from being defaults.

I'm not sure how one would go about confirming that this service is still pro bono and not malicious, and whether it's likely to stick around in the future.

[1] https://github.com/cjb/serverless-webrtc/blob/master/js/serv... [2] https://bugzilla.mozilla.org/show_bug.cgi?id=807494 [3] https://bugzilla.mozilla.org/show_bug.cgi?id=920991 [4] https://bugzilla.mozilla.org/show_bug.cgi?id=1143827