"Older versions of Vegas Pro than 14.0 are licensed under a system (as previously used by Sony) which permits use on multiple computers by one user; after an unspecified number of installations on different or updated PCs you may need to contact support to reset your "installation count"." (From this FAQ item 9.)
VEGAS_EricD wrote on 9/14/2016:
The current Sony EULA stipulates the license is for one user, it can be installed on 2 PCs for the same user, and cannot be used used on 2 or more PCs at a time.
"Sony grants you a limited license to use the Software on two (2) computers or mobile devices, as applicable; provided that the Software may not be used on two (2) or more devices simultaneously".