Hi Jason,
That is correct that you need to re-apply the license to the server every 90 days, but that is different than the perpetual license. The server works on a license key that unfortunately expires every 90 days but it is a very simple, straightforward, process to regenerate the key, this document describes the process. The perpetual license essentially gives you right to regenerate this key again and again to keep your SAP HANA system running for your development.
I hope that is clearer now.
Rocky