Several of the cores here are written with a language called "bluespec". I've looked at bluespec.com and come away none-the-wiser, other than that it apparently compiles into verilog. The makefiles for the projects using it all seem to assume that the tools are installed in a standard location, apparently designed for a build system that is available at MIT. Where do the rest of us get a compiler from?

at Bluespec forums you can find the compiler for download. But the license might be a little more difficult to get.