this might help:
http://www.aaxnet.com/topics/slicense.html

Example:
http://www.w3.org/Consortium/Legal/2...tware-20021231

GNU my favorite:
http://www.gnu.org/copyleft/gpl.html


As for the rest of your question, like prodcut key and Demo version .. this is completely up to the programmer or the mother company of the program .... they can either make demos for demonstration and testing or not .... As for the product key ... each product MUST have a key for registration .... today many companies shift to online product registration .....