Firstly an important point that is not part of your question but you do need to know about it:
Make sure that your new VTL is NOT confugured to emulate a physical library. This is because the VUDO license will only correctly activate against libraries that are seen with the supported (as listed in the HCL) inquiry strings for a VTL and you wil be switched to LEO licensing if you emulate a physcial library.
Now for your question: which kind of has two parts
1) Technically will a single VUDO license work with two separate VTL devices configured on the same Backup Exec server without giving license alerts or disabling backup activity. To be honest I could not find any records of cases, forum posts or internal engineering requests that cover this scenario so a test would be needed to confirm what happens. One thing I can say is that as you have been running VUDO for a while already, any trialware timings will have long since expired and additionally once you enter one specific option or agent license you cannot trial the same type of license on the same server (unless you remove the license but you will then have already exceeded the trialware period)
2) Assuming that we do not technically stop you running backups as long as you have one VUDO license, then legally are we going to insist you have a license when you are in effect doing a rolling upgrade. Well the BE 2014 licensing guide (http://static.symanteccloud.com/estore/resources/en/be-2014-licensing-guide.pdf) is slightly clearer than the BE 15 one against this point as it shows an eample of 5x VTLs where you would need 5 licenses (but is not talking about a rolling upgrade) In reality unless you are proved to be running this rolling upgrade for an extended, longer than realistic timeframe for a rolling upgrade then it is unlikely that we would take any legal action against you but you probably will need to check this with our licensing team as suggested by pkh. Also if there is a technical block i.e point 1) that counts the number of separate VTLs then the legal question becomes unimportant anyway.
