Oracle provides Siebel Sample Tools and Client installation with a unlimited License key already embedded in the DBF. You do not need to get the license renewed for that. You can download the same from eDelivery website @ edelivery.oracle.com. But they do not have Siebel 8.0 listed anymore and you will have to download Siebel 8.1 version.
However, if you are using Siebel Business Applications for commercial use then you need to contact Oracle support for the requisite license keys and renewal.