I figured that out -- looked at the source, and realized that they were complied into the executable. I just got a newer distribution, and made a map directly via gdal_contour, by creating shapefiles for the major and minor contours. The result is interesting -- I'll compare this new map with that made by dem2topo. I've just started exploring gdal_demo, so I don't know which options exist to smooth the contours, etc.
A bad thing about gdal_contour: it leaves blocky angular lines at the finest scale (no smoothing for contours, so it seems -- so far). The good thing: you can directly handle much larger maps than you could by dem2topo -- a 10812x10812 geotiff, for example.