Thanks! It's not on GitHub because I don't desire for it to be redistributed by others. I will be releasing a downloadable desktop version (as a Progressive Web App) with even more features for a nominal one time payment. It makes the most sense to do it this way because having some monetization is good motivation to keep improving the product, while people still getting the benefits of running it completely locally.

Besides, most people working with PDFs aren't developers who wouldn't be able to host it locally on their own.