I do have contact with him, so I will have a talk to him about it. And yes, I totally agree that SDSME should be made open source. After all, it's the most vital part for importing the 3D models of maps and to also edit movements as well. Also, there's many bugs in the code that need to be fixed, which is why a lot of people are having trouble using it.
Tools are often the starting point for ROM Hackers, before they move onto learning the hexadecimal values in machine code within the ROM itself (or it's files within). So that's why it's important that we have a stable and open source map editing tool that can encourage others (including people that do 3D modeling) into Nintendo DS ROM hacking.
Heck, even 3DS ROMs are already being modified. Mario Kart 7 is one of them.