Apple allows anyone with an Apple ID to install apps they’ve built themselves onto their devices for testing. AltStore uses your Apple ID to communicate with Apple's servers on your behalf and perform the necessary steps to prepare your account for installing apps onto your device.
Why does it say my apps will expire in 7 days?
Unfortunately, apps that have been installed using non-developer Apple IDs (in other words, Apple IDs not tied to a $99/year Apple developer account) are only valid for 7 days, at which point they will no longer open. To compensate for this, AltStore will periodically attempt to refresh your apps in the background, and you can always manually refresh your apps from within AltStore.
Yeah, in fact, if you have the $99 account you don't even really need AltStore, you can just download the IPA files you want and sign them manually (with Xcode or if you want a less clunkly solution, iOSAppSigner or AltDeploy or a tool like that) and they will last for a year, which is certainly not too much of a hassle to have to resign.
Why do you need my Apple ID?
Apple allows anyone with an Apple ID to install apps they’ve built themselves onto their devices for testing. AltStore uses your Apple ID to communicate with Apple's servers on your behalf and perform the necessary steps to prepare your account for installing apps onto your device.
Why does it say my apps will expire in 7 days?
Unfortunately, apps that have been installed using non-developer Apple IDs (in other words, Apple IDs not tied to a $99/year Apple developer account) are only valid for 7 days, at which point they will no longer open. To compensate for this, AltStore will periodically attempt to refresh your apps in the background, and you can always manually refresh your apps from within AltStore.