You'd need to impliment your own system, like we do with our software. (See scroggle or Plethos at
www.interaktiv.co.uk)
Use a unique ID such as the one built into Opus and use this to compare to your unlock code. For eaxmple:
UID = 12345
JJ HIDDEN code = 9876
Unlock code is 12345*9876 = 121919220
This is avert simple example as it would be easy to work out the key gen, but you could use a hash such as MD5 as this is possilbe with PHP and there are DLLs that can be used with Opus
Therefore md5(121919220) = d41d8cd98f00b204e9800998ecf8427e
Because it's oneway encryption, it's unlikely that somebody could work out the JJ Code to create the key.
Mack