mpweiher, you are correct! PSPDF is a pdfium lipstick. You can find its license in binary sdk-s or simply ask them. Included or derived work must be disclosed!

Also using the pdfium via Enscripten is not news (https://github.com/coolwanglu/PDFium.js is 3 years old).

On commercial, battle tested side PDFTron offers PDFNetJS & WebViewer for years https://blog.pdftron.com/2015/11/10/pdfnetjs-html5-pdf-viewe... (http://xodo.com/app is the demo referenced in the presentation).