Apple is charging developers money to avoid a problem imposed by Apple themselves. To be fair, the developer subscription includes tools and documentation for

Apple is charging developers money to avoid a problem imposed by Apple themselves. To be fair, the developer subscription includes tools and documentation for Mac/iOS specific development that a price tag is fair for. But for the use case of cross-platform (e.g. Java) open-source development, not even a standard CA-rooted code signing certificate allows distribution without the security error. You have to pay Apple for one, or else your app is 2nd class and your users need workaround instructions.