Dullard alert. I'm confused. 
No surprises there.
When you buy the DVD version of City Navigator and it is "locked to one device". Exactly what "device" are we talking about. PC or GPS device ? If PC how do you get it on your gps device and use the maps ? If GPS device how does it know to lock to the GPS device ?
When I last bought maps you could download the DVD onto one or more PCs so you can see the maps "at base" so to speak. Then you can create a code to unlock the maps on one specified GPS device, so you can use them on your PC and on the one GPS device.
Unless things have changed (and in fairness it's been several years since I bought any Garmin maps), if you buy the DVD you can use the maps on any number of PCs but only one GPS whereas if you buy a microSD card you can move it between GPS units freely but may not be able to use the maps on a PC.
Locking to the GPS device is based on generating an activation code, and presumably a central database records that your serial number has been used to generate an activation code so won't give you another one. I'd assume something in the unit's firmware looks for something within the files - if you transfer maps onto a different device the transfer will go ahead as expected but the device will report an error on startup and won't read the maps.
Last I checked (about 2011, when I bought my Montana) there is no facility to transfer maps from one unit to another, so if you buy a new GPS you have to buy a whole new license for any maps you want to keep. I realise Garmin don't make the rules regarding map licensing but I would have thought they are a large enough customer of the people that do that they could bring a bit of pressure to bear so people could at least pay an upgrade price rather than having to pay the full price all over again.
