ICBM 2009a nonlinear symmetric template (mni_icbm152_*_tal_nlin_sym_09a), as distributed with nilearn 0.14.1.
Used in Learn Cerebral v0.5 to build the cortex, cerebellum and brainstem surfaces (grey + white matter probability maps), fitted to each patient by affine + SyN registration.
Fonov V, Evans AC, McKinstry RC, Almli CR, Collins DL. Unbiased nonlinear average age-appropriate brain templates from birth to adulthood. NeuroImage 2009;47:S102. Fonov V et al. Unbiased average age-appropriate atlases for pediatric studies. NeuroImage 2011;54(1):313-327.
Licence text (as published with the ICBM152 2009 templates, via TemplateFlow tpl-MNI152NLin2009cSym/LICENSE):

Copyright (C) 1993-2004 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.