Why should I buy fman?
You should buy fman because you think it's cool and you want it to continue. Other file managers stopped because they ran out of funds. fman currently makes $400 per month. That's too little to sustain the full-time development behind it. If you like fman, please get a license. It only takes 30 seconds.
Why are there no free updates?
Other apps charge for major versions and give you minor updates for free. This creates a bad incentive: To sustain revenue, vendors have to create ever more revolutionary (and often backwards-incompatible) major versions. fman on the other hand only charges for what you get. This way, it can evolve smoothly and continuously.
Is there a lifetime license?
With a lifetime license, you (the customer) would bet that fman is maintained forever while I (its creator) would bet that development eventually stops. That's a terrible alignment of interests. You want me to keep updating fman, and I want to be able to pay my bills while doing it. No arrangement captures this better than a subscription. For this reason, there is no lifetime license.
Your question isn't answered here? Get in touch!