/usr/include/osl/ is in libosl-dev 0.6.0-3.1.
This file is owned by root:root, with mode 0o755.
There are a lot of files here (496 total). We're only showing the immediate contents of /usr/include/osl.
/usr/include/osl
..
/usr/include/osl/annotate/
/usr/include/osl/boardTable.h
/usr/include/osl/c/
/usr/include/osl/centering3x3.h
/usr/include/osl/centering5x3.h
/usr/include/osl/checkmate/
/usr/include/osl/config.h
/usr/include/osl/container/
/usr/include/osl/direction.h
/usr/include/osl/directionTraits.h
/usr/include/osl/effect/
/usr/include/osl/effectContent.h
/usr/include/osl/effect_action/
/usr/include/osl/effect_util/
/usr/include/osl/enter_king/
/usr/include/osl/eval/
/usr/include/osl/game_playing/
/usr/include/osl/handicap.h
/usr/include/osl/hash/
/usr/include/osl/misc/
/usr/include/osl/mobility/
/usr/include/osl/move.h
/usr/include/osl/moveLogProb.h
/usr/include/osl/move_action/
/usr/include/osl/move_classifier/
/usr/include/osl/move_generator/
/usr/include/osl/move_order/
/usr/include/osl/move_probability/
/usr/include/osl/neighboring8.h
/usr/include/osl/ntesuki/
/usr/include/osl/offset.h
/usr/include/osl/offset32.h
/usr/include/osl/oslConfig.h
/usr/include/osl/pathEncoding.h
/usr/include/osl/piece.h
/usr/include/osl/pieceStand.h
/usr/include/osl/pieceStandIO.h
/usr/include/osl/pieceTable.h
/usr/include/osl/player.h
/usr/include/osl/progress/
/usr/include/osl/ptype.h
/usr/include/osl/ptypeList.h
/usr/include/osl/ptypeList.tcc
/usr/include/osl/ptypeTable.h
/usr/include/osl/ptypeTraits.h
/usr/include/osl/rating/
/usr/include/osl/readme.h
/usr/include/osl/record/
/usr/include/osl/repetitionCounter.h
/usr/include/osl/search/
/usr/include/osl/sennichite.h
/usr/include/osl/square.h
/usr/include/osl/squareCompressor.h
/usr/include/osl/stat/
/usr/include/osl/state/
/usr/include/osl/stl/
/usr/include/osl/template.h
/usr/include/osl/threatmate/