Is it illegal for a proprietary platform to host user created-content that was originally uploaded to a public website?

Context: I believe my Anki (https://apps.ankiweb.net/) deck was converted into a Reji (https://reji.me/) deck and used in their premium (must pay for) application.

1) Is it legal for other companies to use open source Anki decks as part of their own content that users must pay for? Here are the legalities but I'm not confident - https://ankiweb.net/account/terms

"In addition to the license you grant us above, you may optionally grant users extra rights by specifying so in your deck's description, such as allowing them to redistribute modified versions of your deck. You may not impose any extra restrictions." This tells me that I cannot actually prevent the distribution of my deck. Is this a correct interpretation?

2) Would this have been illegal if Reji simply allowed their users to upload their own (from their local computer, so it could be anyone's) Anki decks onto their own personal Reji app (not public for Reji users to consume)?

3) What about onto Reji's shared deck market place (just like Anki has) for others to consume? And what if instead of another user uploading my deck, I actually did (nefariously)....would this still be illegal?