Author of Sloth here. I develop free software in my spare time and I'm not willing to pay Apple USD 100 per year for the "privilege" of developing for their platform. It's a sad state of affairs when independent developers like me have to shell out hard cash in order to give software away for free. True, USD 100 isn't much, but I'm opposed, on principle, to paying money to an enormously wealthy megacorporation just to make software for their platform. Not so very long ago, macOS had a vibrant independent developer community. It's now slowly being choked to death with this horrid App Store stuff.