As I said before, the tool is public domain. You can do anything you want with it, without even asking for my permission. And you don't have to give credits.
So please, release your code on github.
May I see what a "L3DT climate file" is? I just had a look at the second chunk in terrain.data (which contains textures) and it doesn't seem overly complicated: each terrain layer just contains a list of all the triangles that are painted with this layer's texture. If you can decompose your climate file in texture layers with one grayscale image per layer, you should have no problem importing it in DOS.
