I am about to purchase a development kit with a device locked license. However, I will have my own prototype with a different package and speedgrade. Will my device locked licenses also work for a device with same stem number (e.g., XC6VLX240T) but with different package and speedgrade?
"Device-locked" means locked to a particular device, regardless of speedgrade or package.
For example, the ML605 has a device-locked version of ISE Design Suite: Logic Edition, locked to Virtex-6 LX240T FPGA. That license can be used with any LX240T device, regardless of the package it comes in.