There’s a “free” version that offers a limited exposure to the features but since you’ve got a library already established that may not be the best choice.
Infuse is offered in two versions, the stand alone V6 Pro that is a one time purchase and covers all future updates made to V6 but when V7 rolls out that would be a new purchase.
The other option is to go the subscription route. Then as long as you have a current subscription you will get all updates at no charge including major versions like V7, V8, etc.
There is a post that goes over these options and I believe also details some of the specials for trial offers if I remember correctly