I realize this is old, but you could just have an MST file place the license for you. Also, if the License file is a one liner, it may be smarter to create the file instead of copying it, such as:
%ComSpec% /c echo LicenseKey=1234567890 > %ProgramData%\mypath\license.lic
Since you're getting access denied, I would venture to say that you're accessing a \\server\share as the System account and have not give Domain\ComputersGroup access to your share. The AD Computer objects have to have permission to the share, since that's what account the System accounts authenticates as.