The "Free Download" advertisements often referred to legitimate promotional giveaways:
Iris 2 utilizes spectral filtering technology originally introduced in iZotope's RX restoration software. While there isn't a specific paper titled after the Iris 2 advertisement, the "two-stage spectral model" is a common academic topic for sound texture perception and synthesis.
Version 2.02c was an update specifically for macOS 10.15 (Catalina) support.
iZotope maintains a research team that publishes scholarly papers on the underlying technologies used in their software, such as spectral processing and audio separation.
Note that there is a separate academic tool called IRIS 2+ used in solar physics research to recover radiative losses in the solar atmosphere. This is unrelated to the iZotope music software. Product Documentation and Version Details
iZotope officially discontinued Iris 2 in 2022 and it is no longer available for purchase from their main site. Support Notice for Iris 2, Breaktweaker, and Trash 2
Detailed operation for spectral filtering and sample-based synthesis is found in the iZotope Iris 2 Reference Manual . Free Download History (Advertisements)
A well-known advertisement offered Iris 2 (valued at $149) for free with any purchase or via a specific coupon code during limited-time promotions.