Key rekordbox

The CDJ-350 does not ship with a license key for rekordbox DJ; it may have had a key for rekordbox v2, which was the last version requiring an activation key for rekordbox in general, but v3 and v4 are both free to use the software without a key.

Where you would require a key to unlock performance mode (aka rekordbox DJ) where you can use a hardware controller to mix the audio within the software.