In very general terms, some say that if the author is selling his lectures, music, or computer program or the like, then there's a Halachic copyright. As such, it is a form of stealing to use the product without paying for it. If he is not selling it, however, or he doesn’t have any copies to sell, or you are not a potential costumer, the issue of a Halachic copyright does not apply. <ref>Rabbi Hershel Schachter in a [http://www.yutorah.org/lectures/lecture.cfm/788264/Rabbi_Hershel_Schachter/Copyright_Law shiur on yutorah.org, titled Copyright Law]</ref>
The poskim discusses whether there is a real ownership of an intellectual property. Shoel Umeishiv 1:44, Rav Shimon Schkop Bava Kama siman 1, Netsiv in Meishiv Dvar 24 hold that there is a halachic ownership of intellectual property, while the Mishpatei Shmuel 35 and Bet Yitzchak YD 75 argue that there's no ownership of intellectual property. See Shurat Hadin v. 16 p. 290 n. 13 and Yabia Omer CM 7:9.
* [http://www.yutorah.org/lectures/lecture.cfm/788264/Rabbi_Hershel_Schachter/Copyright_Law Rabbi Hershel Schachter in a shiur on yutorah.org] titled Copyright Law