Multiple OTP Tokens for the Same User
You can assign as many YubiKeys and OATH tokens as you want to each user account, and they will all operate interchangeably. Each key will be programmed with its own distinct randomly-generated secret. So the loss or compromise of one key does not implicate any other keys the user still carries.
Each user account "takes up" only one AuthLite user license, no matter how many OTP tokens you assign to them.