mni152-2mm.nii.gz is the ICBM 2009c Nonlinear Asymmetric MNI152 template,
brain-extracted T1-weighted image at 2 mm, as distributed by TemplateFlow
(tpl-MNI152NLin2009cAsym_res-02_desc-brain_T1w.nii.gz), copied unchanged.

Source: https://www.mcgill.ca/bic/icbm152-152-nonlinear-atlases-version-2009
        https://www.templateflow.org/

Copyright (C) 1993-2009 Louis Collins, McConnell Brain Imaging Centre,
Montreal Neurological Institute, McGill University.

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies. The authors and
McGill University make no representations about the suitability of this
software for any purpose. It is provided "as is" without express or implied
warranty. The authors are not responsible for any data loss, equipment
damage, property loss, or injury to subjects or patients resulting from the
use or misuse of this software package.

References:
  VS Fonov, AC Evans, K Botteron, CR Almli, RC McKinstry, DL Collins and
  BDCG, Unbiased average age-appropriate atlases for pediatric studies,
  NeuroImage 54(1), 2011. doi:10.1016/j.neuroimage.2010.07.033
  VS Fonov, AC Evans, RC McKinstry, CR Almli and DL Collins, Unbiased
  nonlinear average age-appropriate brain templates from birth to adulthood,
  NeuroImage 47 (Suppl 1), S102, 2009. doi:10.1016/S1053-8119(09)70884-5

zstat-4mm.nii.gz is simulated data (smoothed Gaussian noise inside the
brain), written by neuroim2 in software/showcase/neuroimjs/make-data.R.