This is the Quake III: Arena BSP-to-AAS compiler.
You can download the latest version here.
Straight from the source:
Usage: bspc [-<switch> [-<switch> ...]] Example 1: bspc -bsp2aas /quake3/baseq3/maps/mymap?.bsp Example 2: bspc -bsp2aas /quake3/baseq3/pak0.pk3/maps/q3dm*.bsp Switches: bsp2aas <[pakfilter/]filter.bsp> = convert BSP to AAS reach <filter.bsp> = compute reachability & clusters cluster <filter.aas> = compute clusters aasopt <filter.aas> = optimize aas file aasinfo <filter.aas> = show AAS file info output <output path> = set output path threads <X> = set number of threads to X cfg <filename> = use this cfg file optimize = enable optimization noverbose = disable verbose output breadthfirst = breadth first bsp building nobrushmerge = don't merge brushes noliquids = don't write liquids to map freetree = free the bsp tree nocsg = disables brush chopping forcesidesvisible = force all sides to be visible grapplereach = calculate grapple reachabilities
File a bug report if you run into issues.