For those looking for an MIT alternative, there's an embeddable solution which uses PDFium (Apache) compiled to wasm instead of MuPDF (AGPL): https://www.embedpdf.com/

There's a hosted version for quick edits: https://app.embedpdf.com/

Discussion from several months ago: https://news.ycombinator.com/item?id=44901683

Neither fully handles XFA, but that's a perennial struggle.