From the Library Elf website:
For the past five years Library Elf has been helping library patrons keep tabs on their library material. It is an independent service and not related nor funded by libraries. Costs have gone up greatly (new server, higher bandwidth, etc.) and to help pay for the new costs, we are implementing two levels of service: basic service which is free, and a premium service which is subscription based. If you have gotten good value out of Elf in the past, we hope you will help support Elf by subscribing to the premium service.
I’ve gotten a lot of good service from Library Elf and have just signed up for the one-year account for $12 – a no-brainer for me.