I believe I was thinking of https://github.com/rileytestut/AltStore, but I’m not sure if that’s the exact project (I don’t use iOS, so I don’t keep all of the details in mind)
Quoting their FAQ:
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.
Quoting their FAQ:
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.