Are the following PHP generators viable alternatives to the Jar files needed for some export formats?
phpMobi file generator
PHP ePub generator
Hi @sswettenham, we use KindleGen and EpubCheck, both of which are independent binaries. We have enough trouble with the idiosyncrasies of the Kindle format that I would not be confident in an “experimental” third-party generator, particularly one that has not been updated since 2016. As for EPUB, we actually generate the files entirely using PHP; EpubCheck just validates the output to make sure that it conforms to the standard (and facilitates reliable transformation into Kindle/MOBI files).
EDIT: I guess that is a “no” 
From the phpMOBI repo:
IMPORTANT: Do NOT use this on a public web server: most of it was coded in a weekend, with no testing and no special attention to security. Also, as no official documentation for the MOBI file format is available, there will be some bugs/problems in the generated files…
Thanks,
Exploring alternatives of having external dependencies to WordPress.
Ideally we would love if we had less of these, so thanks for digging into it.