http://backup.ninjaloot.se/share/map2obj.zipSince I've had absolutely no time to work on this lately I haven't made any progress with the normals so as promised I am releasing a version that otherwise works fine but will set all normals to point straight up. Not really noticeable in game but if you do use this version make sure to keep a copy of the obj file so you can re-export it whenever I find a solution to this problem.
The programs are both command line tools and they both take a single parameter.
For map2obj it is the map file from which it will produce a wm.obj and wm.mtl in the current directory. To make textures work properly you will have to extract them yourselves, wm.mtl writes the names as .jpg but if your modelling tool supports png it should still work if you just rename the .png files.
For obj2map it is the obj file which will be converted into a set of WM0.MAP and WM0.BOT files, the mtl file is not used and textures do not need to actually exist for this to work.
Only WM0 is supported at the moment but it should be fairly easy to add support for underwater and snowfield in a later version.
Be careful with what kind of changes you make to the .obj file, the original coordinate system must be kept intact and objects must cover their respective square area. Also old(er) versions of blender may not be able to import/export the .obj file at all without mangling it too much.