The rent is not for the software but for some additional service or hardware that you incur in making it available. As long as you provide some service other than just licensing the software.
As an open source creator, you essentially are giving away your labour to the community as charity. This is done out of free will and is not an obligation. There is no obligation whatsoever to support and provide guarantee either to any user. This distinction is where most open source contributors feel burnt out. As an open source creator, I look as community requests as "feedback" and not something I am obliged to do. When we take payment to provide certain guarantees or services, that is when it enters the realm of services and is not connected to the software at all. Anyone capable can do that. The company publishing the application has an head-start. That is all.
That is the mindset where it works as a public asset, rather than a "source available" or other kind of program.