Copyright (c) 1998 Rob Nelson

BOKU is played on a 5x6 hexagonal board with 36 stones for each player (so, a total of 72 stones to occupy 80 empty cells).

MOVE - A player drops a stone on an empty cell
KO - If a player makes a capture, the opponent can not immediately play in the same spot.
CAPTURE - A player captures one of two stones any time he sandwiches those stones between a pair of his stones.
GOAL - A player wins if he gets five or more stones in a row.

BOKU is remarkable simple, but according to David Glaude and other players, the game is, at best (due to limitations on board size and number of stones) a draw. With less restrictions, BOKU is probably a win for first player (like Gomoku and Pente without opening restrictions).

An example

White's turn. He must drop a stone at cell [1], or Black will win with a 6 in a row. After that, Black may drop a stone at [2], capturing the marked white stone or stone at [1]. 

If the stone at [1] is captured, White cannot play there (Ko rule) and Black wins.

In UK the game is manufactured by the London Game Company.  David Glaude has a webpage dedicated to BOKU, where he presents much more information about the game. There are also an article and some pictures [I II] related to the game at MSO.