What is the ruling on publishing copyrighted books that are still being sold, or those whose authors have passed away, or translated books, or those that are out of print but their copyrights are reserved? Is the publisher of the books sinful if he is unaware of the ruling?

There is no objection to publishing beneficial religious books on websites, provided that their owners or those in charge of them do not prohibit it, because intellectual property rights are legally recognized in Islamic law, whether their owners are alive or deceased, or if the books are translated, or old and out of print. There is no sin upon whoever published books before knowing that this is prohibited by Islamic law.