/usr/share/acl2-6.3/books/taspi/tree-generation/ is in acl2-books-source 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/taspi/tree-generation/branch-and-bound/
/usr/share/acl2-6.3/books/taspi/tree-generation/branch-and-bound/bandb.lisp
/usr/share/acl2-6.3/books/taspi/tree-generation/distance-based/
/usr/share/acl2-6.3/books/taspi/tree-generation/distance-based/naive-quartet-method.lisp
/usr/share/acl2-6.3/books/taspi/tree-generation/heuristics/
/usr/share/acl2-6.3/books/taspi/tree-generation/heuristics/do-search.lisp
/usr/share/acl2-6.3/books/taspi/tree-generation/heuristics/spr.lisp
/usr/share/acl2-6.3/books/taspi/tree-generation/heuristics/tbr.lisp
/usr/share/acl2-6.3/books/taspi/tree-generation/tree-gen-helper/
/usr/share/acl2-6.3/books/taspi/tree-generation/tree-gen-helper/basics.lisp