This is the approved USGS MODFLOW 6.6.0 release.
Langevin, C.D., Hughes, J.D., Provost, A.M., Russcher, M.J., Niswonger, R.G., Panday, Sorab, Merrick, Damian, Morway, E.D., Reno, M.J., Bonelli, W.P., Boyce, S.E., and Banta, E.R., 2024, MODFLOW 6 Modular Hydrologic Model version 6.6.0: U.S. Geological Survey Software Release, 19 December 2024, https://doi.org/10.5066/P1DXFBUR
Visit the USGS "MODFLOW and Related Programs" site for information on MODFLOW 6 and related software: https://doi.org/10.5066/F76Q1VQV