I'm pretty sure Ivan wrote his programs in Delphi or something Delphi-related. Same language as Soldat.
Quick answer: Any programming language which can handle folders, files as output/input streams and GUIs can be used to make a config program.
Java has easy graphics features, and what's done in C++ is easily transferable to Java. So, a Java config program shouldn't be too hard if you know some C++. Also, Bman made a config program in Java for his Ultimate CS Mod.
C++ is more portable and faster than Java, though. C++ programs can be compiled and ran on Windows, Linux (Ubuntu) or Unix (Mac OS) based OSs.
I wish I could help you more, but the problem is, I have no idea how to do GUIs with C++. I think
Dev-C++ can make GUIs, but I need to experiment and right now I feel lethargic. Besides, I'm trying to make my own config program. All I need to do is figure out how to do GUIs and folders.