Federico:
Kalimantan, strictly speaking, refers to the Indonesian (previously Dutch) portion of the island formerly called Borneo. That would exclude Malaysian (previously British) "Northern Borneo," now referred to as Sarawak and Sabah, and the independent state of Brunei.
When Mr. van Zonneveld speaks of Kalimantan, I think he refers to the Indonesian portion of Borneo because Indonesian weapons are the focus of his book. Perhaps he could comment again here, as he has in the past, to settle any confusion.
Ian.