ultra_outliner is free software. Starting from v.0.9.12 it requires personalized license, that you can request from license server absolutely for free.
In order to request it, just start ultra_outliner and follow instructions. After requesting license will come to your mail and you need to copy it into dialog window. In case you have any problems please contact support.
There are no restriction on licenses you have. You can request as many licenses as you want.
License is bind to hardware you use it on. It uses unique hash of MAC address, HDD and system IDs as a fingerpring, so in case you change your hardware - you might need to renew your license. License is signed with RSA and can't be modified once issued by license server.
License is used in order to assign authorship of document changes. It is important step for multi-user document editing. Secondary it helps us to understand the amount of real users.