ISE 3.1 is out now, with full source code, binaries for all platforms. Download now (107.8 Mb):

SourceForge ISE 3.1

ISE 4.0 and the source code for ISE 3.1

The source code for ISE 3.1, and the newer ISE 4.0, currently under heavy development, is available as a GIT repository  here.

If you wish to assist with bug patching, branches etc.., please contact me for access.