/usr/include/osl/move_classifier/ is in libosl-dev 0.6.0-3.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/osl/move_classifier/attackDefenceAroundKing.h
/usr/include/osl/move_classifier/blockLongEffect.h
/usr/include/osl/move_classifier/canAttackInNMoves.h
/usr/include/osl/move_classifier/check_.h
/usr/include/osl/move_classifier/classifier.h
/usr/include/osl/move_classifier/classifierTraits.h
/usr/include/osl/move_classifier/directCheck.h
/usr/include/osl/move_classifier/kingOpenMove.h
/usr/include/osl/move_classifier/moveAdaptor.h
/usr/include/osl/move_classifier/openCheck.h
/usr/include/osl/move_classifier/pawnDropCheckmate.h
/usr/include/osl/move_classifier/readme.h
/usr/include/osl/move_classifier/safeMove.h
/usr/include/osl/move_classifier/trapRook.h