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Am I the only one who hates these fake PDFs?
(eclecticlight.co)
If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.
Adobe does sell licences for other companies to use the XFA format but even the software you linked has a free reader that pushes you to the paid full version. Also not FOSS.