Apples licensing is on a 'per user basis', not 'per system', as you seem to suggest. And, it's only a copyright violation if the OP is planning on copying the disk for someone else.
Hmm.. I tell you what I do know. You can't make a older system installer disk work on a newer system from the same line. However, it might be possible to make a newer system disk work on a older system from the same line.
Then again...
It'll depend on the OP's disk. If it's the latest retail version, then it'll work on all Mac, old and new with the exception of some PowerPC systems.