In legal terms: Plausible deniability, or the very good act of such.
In moral terms, it depends on your own personal interpretation. If you are collecting it from the buffers on your video card, or as it passes through YOUR computer, just like with any information on the internet, then it belongs to the computer memory, and therefore the owner of that memory. You.
You can also look at it from this perspective: what is its value. Is it something that is saving you a lot of time, or a little bit of time. Is the quality of the object something you would feel bad if another got a hold of? Are you losing any money because of it? If you would feel sorry if you hurt another person over it, then don't do it. If you feel you have no reason to believe an individual would be hurt, any individual from a larger company, etc, then what is the harm, except if they come after you over greed?
Do you feel like you are robbing somebody at gunpoint? Or maybe just sneaking into their house? Or are you just making a modification to the wheel, which we all know nobody has a patent on of any meaningful value.