I assume you mean you want to be able to download it and install it on your own phpbb board.
have you looked at the available styles ( in phpbb they are called styles, not themes ) here in the styles demo:
https://www.phpbb.com/customise/db/styl ... r/demo/3.2
that forumotion style is quite old and has a lot of strange code in it for strictly forumotion stuff .
I would suggest that if you like the colors and layout of that style, that you find a similar one in the demo above and edit it to what you want.