[Rick]

Cannon such as this were indeed used on European ships ; they were known as swivel guns or 'murdering pieces' and were used to sweep the decks of an enemy vessel before boarding . They were indeed made in Europe also ; and out of brass .
I don't think I saw a picture of the cannon entire ; perhaps from a view of the overall piece and its decorations we may determine whether it is of European or Borneo/Moro manufacture .

Edit:

Okay , I scrolled down a bit more and found some pictures of the 'lantaka' in question. The decorations appear to be *very* European in style ; nothing like the traditional okir designs associated with the Moro cultures .

So I'm thinking you've either got an export/trade piece or a Euro murdering piece that wound up being captured or traded to the East . This just doesn't look like native work .

YMMV