A program runs on a specific computer. The program and the computer are individually important. However, it is not important that the program run on this particular computer. We have several computers; it could run on any of them. It just ended up on this one because that's where it was installed.
What word describes the relationship between the program and the computer?
Casual and arbitrary are close, but I feel there's a better word that I cannot remember.
Arbitrary and coincidental feel like luck was involved, or it is some manner of accident.