The above program , if used properly, is legal IIRC. Since the format for the mesh files has been made public IIRC. There are plenty of programs that already edit the MSTS shape files anyway. However, as it allows you to convert an exported .s file, it is a very 'grey area' type program. If someone were to use it irresponcibly, it would lead to a lot of trouble. But, used responcibly, it is a very useful program. I myself have converted a number of items WITH PERMISSION. None released yet, but they did work...
And that is the main thing. Get permission before you do ANYTHING.
Zec