The Software Preservation Society (SPS), formerly the Classic Amiga Preservation Society (CAPS), dedicates itself to the preservation of software for the future, namely classic games.
This organisation uses its own file format called IPF (Interchangeable Preservation Format) to create backup images of each disk it collects. This is similar in nature to ADF, but the idea is that all disks are original as possible, as they were delivered from the developer, and none are cracked/pirated copies of games that have been tampered with and altered. In contrast when you obtain a game in ADF format it is often a cracked version with a pirate group's cracktro at the start.