I created Licentra, an open-source tool, to handle software (SaaS) subscriptions in a way that benefits both business owners and their customers.

SaaS owners design the billing that completely shut users out when they stop paying, which I've always found annoying because it undermines trust.

With the help of Licentra, customers can always maintain a working copy of the software granting them perpetual access to the most recent major version they paid for. Additionally, it permits you to continue sending them patches to maintain the stability of their previous version, but it automatically prevents them from accessing major feature upgrades until they resume paying.