I think it's great that you are trying to make your software available to individual developers and open-source projects
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I saw the announcement about a month ago, and if you do not mind I'll try to explain why I chose not to use your offer.
Much of what I write is (open-source) libraries, which other people hopefully will be able to include in their projects. While I might not mind adding a blurb to the README saying "This project uses so-and-so to provide this-and-that (link)", I do not wish to put advertisement in every single source file, thereby forcing it on my users.
I can see your point about using the advertisement comments as a means to deter large companies from using the free version for their open-source projects, but that also means that they would be less likely to use other peoples open-source projects that did include it. So I would potentially be limiting my user base.
Now I am certain this works great for most people, and if for instance you are developing an application it's great that you are not forcing advertisement into the compiled binary in any way. So thanks for doing this.