Q: Can I copy a book that is no longer in print? What about an older version of a computer program that is not sold anymore?

A: If the product is not available, it would seem that there is no concern of hasagas gevul (encroachment). Furthermore, even according to opinion that halacha recognizes ownership of intangible intellectual property, the creator might not mind copying here; it would be like yei'ush and avaiedah midaas (willful abandonment).

On the other hand, if the product is available in a newer version, the old content remains in the new version with additional features. Thus, Rav Y.S. Elyashiv zt"l does not allow copying the older version. It also continues to be prohibited based on dina d'malchusa.

If you purchased a license for the current version, but prefer the older version for some reason (e.g., it requires less memory or you're familiar with it), you are allowed to copy the older version. However, if you purchased a license for the older version, you do not have the right to copy a newer version; it would be like copying any other program.

(See Emek Hamishpat, Zechuyos Yotzrim, Intro. 3:38-40:5-9; ch. 35:200)