So when are?
If you know it is illegal when you do it, then, it is a mortal/grave sin.
When its illegal its theft and that is a sin of grave matter.
Although how does abandonware play into this? Such as ROMs for NES games that aren’t produced anymore
As others pointed out it is related to the sin of theft.
However for it to become mortal the damage that you are inflicting on the offended party must be grave.
If the game or software you downloaded is no longer in production and therefore you cannot purchase it, it is difficult to associate any damage being inflicted to any one.
Also one must be aware that even copyrighted materials have an expiration on the protection afforded by the copyright.
Same applies to patents protecting industrial goods or ideas.
I think wich depend on the value.
Have any place where we can find any theologian talking about that?
In that case, there would be no direct damage to the game developer, but we may still be concerned that it may contribute to a disregard for the law, which indirectly affects many people, primarily developers but also, to some extent, users.
It’s kind of like jaywalking. When I am within sight of children, or near a school, I (almost always) cross the street at the crosswalk. It is not a matter of my own safety; I could safely cross the street anywhere. However, I want to set a good example for kids, and don’t want to undermine the law in their eyes.
I know this is a weak argument, but just thought it would be useful to discuss it.