I thought that not one use it anymore (if it was ever used... at least onf the French wikisource it never really worked well as it didn't understand the 'pages' tag we use on almost all pages) and we have our own PDF/ePub/mobi generator (https://tools.wmflabs.org/wsexport/tool/book.php). SO don't we all use WSexport?

I see very few pages on https://en.wikisource.org/w/index.php?title=Special:PrefixIndex&prefix=Wikisource:Books/ , most of them generated a long time ago, so I don't think that this will have any impact on Wikisource.