After a few days of wrestling with bizarre library name lookup issues, and Cygwin's assembler's lack of appreciation for nice x86 assembler PIC code function declarations, I've managed to get Kaffe building and running largely fine under Cygwin, so that now people can hack on Kaffe on Windows, as well.
That was actually an ocassionally requested feature, in particular in the post-Harmony-announcement rush of good will and volunteers to try it out and see how far along that whole free runtime thing is. And as a lot of people are stuck using a popular, non-free platform, but apparently nevertheless want to help out on free runtimes, ...
The upcoming 1.1.6 will be able to run on Cygwin. See the docs for details.
I'll go back now to preparing the release, and merging in the remaining patches.