Apple is opening up web distribution for iOS apps targeting users in the European Union starting Tuesday. Developers who opt in — and who meet Apple’s criteria, including app notarization requirements — will be able to offer iPhone apps for direct download to EU users from their own websites. It’s a massive change for a mobile ecosystem that otherwise bars so-called “sideloading.” Apple’s walled garden stance has enabled it to funnel essentially all iOS developer revenue through its own App Stor...