Interesting suggestion. I was not familiar with this service.
Maybe an easier approach for developers will be to publish there artifacts as
DonationWare.
I like this idea. . .
I think it makes sense for the developer to still release the app FREE or PAID and also add a FLATTR button. The FLATTR button is like a tip on top of the purchase price that can easily be rewarded long after the purchase. Readers can also reward the developer without actually purchasing the app just to encourage the developer to continue with what they do.
I am not suggesting you add this to the forum though. Developers can quickly add FLATTR as an added source of revenue especially if they have a support website that really in itself does not generate revenue directly separate from the app sale itself.
Just my thoughts on this.
Bob