No. No restrictions should be put on downloads. The main point is that the distribution channels should always be free.

What should be gated and limited is the commercial use: reselling, relicensing, using for business, etc.

> the optional payment (I promise you nobody's gonna do that)

Such "promises" seem to be based on no facts. Moreover, they contradict my personal experience.

I would be very interested in using that business model. In fact, I have already used it with other types of services. I have paid for software that is open source, free to download and free to use. Multiple times. Simply because I like the software and I wanted to thank the authors for it in some tangible way.