There is a book written by Rabbi Moshe weiner called the divine code where he explains the noahide laws. Is spreading this ebook considered gezel / theft? I think that it is but I could use sources and expert opinion.

Shalom, Thank you for your question. Most books published today have copywrite issues, which automatically create an obligation under Jewish law to respect them. This concept is called “the law of the land is [also Jewish] law” (dina d’malchutah dina). There are lengthy discussions of copywrite issues in Jewish law – but the overwhelming consensus of opinions is that books that are not in the public domain, the secular laws of copywrite apply also according to halacha. May I suggest you turn to the author or publisher and get personal permission to copy and spread the book. Blessings.