A BSP is a simple greyscale image... Just as the DBPro handbook says it is x-d
Basically, you could just use Paint to make a BSP...
Just create something like a relief map of the landscape you want. In greyscale, the areas that are pure white will be the highest point possible, and the areas that are pure black will be at the "ground" on the matrix.
Having yet to actually test how this works, I must ask...
When creating a greyscale, will the white simply go to the Height parameter in your matrix (basically automatically hitting the ceiling of the matrix), or is the height in the BSP calculated according to RGB data?
By calculating it according to RGB data, I mean that the higher the sum of the RGB values (closer toward white), the higher the point is rendered. Of course, this is the way it's probably done either way, but the difference being whether there is a formula for a specific height by RGB value, or whether it is calculated as a percent of the Height parameter.
To even more specifically answer your question, DBPro does include all the 2D commands needed to create your own greyscale in pure code, or even remake Paint into something more friendly toward this purpose. If you really study the DBPro syntax (vocabulary of commands) and semmantics (grammar of commands), you'll see that an application could even be created that would show you the relief map in 3D by rendering it on the fly, as you work on the greyscale.
Keep in mind there are about a thousand ways to do anything. At the moment, the only 3rd party tool you really need is something to render your .x models. Though I am sure there is a way to do that in DBPro, vector editing would still require that a few commands be added to the language via DLL.
Hope I helped some, since I tend to ramble 8)