Hi there,
What would you like to upgrade too? If to BE 2010, you would have to do a multi-step upgrade to get there...
You would use the link below for additional information on how to do this:
http://seer.entsupport.symantec.com/docs/331658.htm
If you upgrade, you can call Symantec, and get put through to the licensing department. They will be able to send you new licenses for what you currently have, if that is covered in your agreement with them.
Anything additional can firstly be trialled for 60-days, and would then stop functioning. You would have to buy additional licenses.
BE 10.x only supports up to Sharepoint 2003...anything newer would see you needing to upgrade.
Laters!