Do you expect an IAP peddler to support free software?

Yes actually: plenty of companies don't care where the money comes from, they're happy as long as there's money. Unity, the other big ad- and IAP-peddling game engine company, has pretty good Linux support.

It's weird for a company to explicitly say, "if you use this one operating system you can go F yourself, we don't want your money". (Note: this is not the same as saying "we only officially support Windows at this time, sorry". There's seething hatred in Sweeney's words.)