I'm already familiar with ViewerJS https://viewerjs.org/ and it's great (have had it on my website for several years).
But I recently came across what's apparently a different one that has a somewhat different look-and-feel. See
for an example. I'd give you its homepage, but don't know what it's called, or anything else about it.
So, question: what's it called? Open source? And what's its homepage (if that's not immediately obvious). Thanks.