Are there other open-source tools on other OSes that can open it? Any programmatic way to manipulate it?
One thing to try is to display a hex dump (or just display it as text, if it is a text format) and see if anything can be figured out from that.
One thing to try is to display a hex dump (or just display it as text, if it is a text format) and see if anything can be figured out from that.