The install process makes it difficult not to register it. You can opt not to have communications from Apple. Some are concerned about Apple collecting information about them and complete the mandatory form with fake information. I am not aware of Apple ever using the information to prosecute for unpaid royalties etc although I do know that one other large computer company does audits of large users of their products.
Thanks for the response. I'm glad to see that there are some "old" Apple users aout there still teaching.
Before I retired, I used to run a small Elementary computer lab and we had to get every program set on the machines with the full registration process to get them to run properly. I usually do the same at home as well. I didn't want to buy a disc and not be able to get the activation code if one was needed.
Only the black CDs/DVDs work on any compatible Mac. Other colours are model specific and will not work on other models. Take care there are many non-black installers out there.
OS X 10.5 does not require a registration code but 'OS X 10.5 Server' needs one.
It may be best to update to Snow Leopard - OS X 10.6
The following is a slightly edited post from elsewhere - I assume the advice is correct:
Apple has OS X 10.5 Leopard replacement media available. Ring 1800-767-2775 (or national equivalent) and talk to a customer service representative. Explain that you have a Mac and need the 10.5 Leopard DVD media replacement. You will be asked for your computer's serial number. It costs about $17.