/usr/include/JAGS/function/ is in jags 4.3.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/JAGS/function/ArrayFunction.h
/usr/include/JAGS/function/ArrayLogDensity.h
/usr/include/JAGS/function/DFunction.h
/usr/include/JAGS/function/DPQFunction.h
/usr/include/JAGS/function/FuncError.h
/usr/include/JAGS/function/FuncTab.h
/usr/include/JAGS/function/Function.h
/usr/include/JAGS/function/FunctionPtr.h
/usr/include/JAGS/function/LinkFunction.h
/usr/include/JAGS/function/PFunction.h
/usr/include/JAGS/function/QFunction.h
/usr/include/JAGS/function/ScalarFunction.h
/usr/include/JAGS/function/ScalarLogDensity.h
/usr/include/JAGS/function/ScalarVectorFunction.h
/usr/include/JAGS/function/VectorFunction.h
/usr/include/JAGS/function/VectorLogDensity.h