Great question, and I'm sure this will come up soon in our ongoing study of the precepts.
For me, I firmly believe that downloading or otherwise receiving copyrighted materials that were not properly paid for (by oneself or even as a gift from another) is stealing. This goes for books, music, movies, etc., because if we participate in such activity, we are stealing from all those that earn their livelihood off of the creation of such materials (authors, musicians, distributors, etc.).
On the other hand, if materials are explicitly made available for free distribution (as many Dharma books certainly are), then that is no problem at all.
Gassho,
Rob
-stlah-
(Sorry for the extra sentence above...).
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