First of all, for the record, I didn’t quote Rav Belsky, I found this piece from Rabbi Moishe Dovid Lebovits (Halachically Speaking) on this site (with help from Cherrybim from the Copying CDs thread.) It doesn’t say that this p’sak is from Rav Belsky, it says, “(footnote 96) Refer to Igros Moshe O.C. 4:40:19.”, and that the piece was “Reviewed by Rabbi Benzion Schiffenbauer Shlita”.
What may be inferred from that Igros Moshe is that it would be midas s’dom for the originator of the recording to be makpid if he does not stand to profit. If I understand correctly, it would still be assur to copy a recording which is currently for sale even if one is certain that he would not purchase it.*
It’s also possible that one is allowed to assume that the original producer is not makpid since he no longer sells it (likely, he would be flattered to know that some people are still interested in his music!).
Regarding Charlie Hall’s point, (possible hakpada for other reasons) R’ Moshe addresses this regarding divrei Torah and says that the maggid shiur may later find his piece faulty and be embarrassed if it’s available publicly. It’s doubtful if that’s the case here, it’s probably just not a marketable item at this point in time.
* A young bachur once told me the following story about himself. He copied his married brother’s CD, rationalizing that it was an unusual style of Jewish music which he would certainly never purchase. His copy broke, so he asked his brother to borrow it again, but it too had broken. He then went to the store and bought it! He then realized that it’s impossible to be certain that a recording that you do find worthwhile to have, you would never buy.