Now, the Catholic Church holds several basic beliefs that suggest intellectual property theft is sinful. The mode of sin can be considered theft, and in some cases, false witness.
First, and however insignificant the effect, intellectual property theft requires the intellectual property creator increase the price of their product to yield the intended income from producing that product. That is, stealing intellectual property drives up the price of that intellectual property for other consumers and/or puts the business at risk. According to the Church, this a form of theft, both from the producer of the IP and the intended consumers.
Even without a measurable hike in price or loss for the business, it breaches the social contract, wherein the intended consumers are placed at an economic disadvantage. E.g., if you, doing your civic duty, pay $1000+ for some useless Adobe suite, only to find that I have a pirated copy; you're going to feel cheated. (So would adobe, if they ever found out.)
Even if it does not contradict the provisions of civil law, any form
of unjustly taking and keeping the property of others is against the
seventh commandment: thus, deliberate retention of goods lent or of
objects lost; business fraud; paying unjust wages; forcing up prices
by taking advantage of the ignorance or hardship of another. (CCC 2409)
Secondly, it is a breach of contract. Whether this is a breach of contract primarily for the illegal distributor or the illegal consumer is debatable. However, any party privy to the existence of a terms-of-use or acceptable-use contract is morally obligated to uphold the terms of that contract.
Promises must be kept and contracts strictly observed to the extent
that the commitments made in them are morally just. A significant part
of economic and social life depends on the honoring of contracts
between physical or moral persons—commercial contracts of purchase or
sale, rental or labor contracts. All contracts must be agreed to and
executed in good faith. (CCC 2410)
Thirdly, the Church teaches that divulging "trade secrets" is an offense against the respect for truth. Applied here, distributing or intentionally accessing the private 1's and 0's that support the livelihood or "private life" of business owners is sinful. And honestly, the best phrase I can come up with to communicate this concept in non-religious lingo is intellectual property.
Professional secrets—for example, those of political office holders,
soldiers, physicians, and lawyers—or confidential information given
under the seal of secrecy must be kept, save in exceptional cases
where keeping the secret is bound to cause very grave harm to the one
who confided it, to the one who received it or to a third party, and
where the very grave harm can be avoided only by divulging the truth.
Even if not confided under the seal of secrecy, private information
prejudicial to another is not to be divulged without a grave and
proportionate reason. (CCC
And lastly, it's not a bad idea to examine the practices of the moral authorities themselves. On the US Conference of Catholic Bishops' website, near the bottom of every page is a copyright notice:
© 2013 United States Conference of Catholic Bishops (usccb.org)
By participating in the copyright system, the US Bishops are clearly condoning leveraging of and adherence to copyright law. And the expectation is clear. If you want to use significant (complete portions) of content from their site, it's reasonable to assume that they expect it be to used only by their permission and according to their terms, per the copyright notice.
A final note: The Church also makes provisions for those whose livelihood depends on stealing.
The seventh commandment forbids theft, that is, usurping another’s
property against the reasonable will of the owner. There is no theft
if consent can be presumed or if refusal is contrary to reason and the
universal destination of goods. This is the case in obvious and urgent
necessity when the only way to provide for immediate, essential needs
(food, shelter, clothing... ) is to put at one’s disposal and use the
property of others.