If you copy the DVD content files (VOB files) on your hard drive and you can open them without issue, it should be fine.
As long as you can read them on your computer without the original DVD inside, it should be good for anyone. I don't think porn DVD were protected, from what I remember.
Can you tell more about your process? If I understand correctly, you create images of DVD (>> .iso or .img files) then you mount them later and play them with the player of your choice, right? (because in this process, the image could be encrypted anyway, the player will decrypt it. But I'm not entirely sure. I always used DVD ripper softwares)