mkwcon is a win32 console utility for encoding and decoding MKW losslessly-compressed files. It supports file-to-file encoding/decoding, encoding from standard input, and nearly-complete decoding to standard output (good enough to get working in shntool). Accompanying this release is shntool 3.0.1 (http://www.etree.org/shnutils/shntool/).
Download mkwcon here (http://www.etree.org/shnutils/mkwcon/).