Sure but who is at fault?

If I manually type an entire New York Times article into this comment box, and Lemmy distributes it all over the internet… that’s clearly a breach of copyright. But are the developers of the open source Lemmy Software liable for that breach? Of course not. I would be liable.

Obviously Lemmy should (and does) take reasonable steps (such as defederation) to help manage illegal use… but that’s the extent of their liability.