Alt.Binz 0.39.4 is the last release available to public. It's freeware. You can use it for free as long as you like.
However, if you think this software is valuable and you want to support it through monetary donations, you are encouraged to do so. By donating you will help the development going. Also you will gain access to future versions of Alt.Binz and you will be able to make feature request that you would like to see in upcoming versions.