I have looked in the archives, the Euphoria home page and Sourceforge. I can
only find ver. 3.1.1.
4.0 is not yet available for download, however, you can check it out from the Subversion Repository, and you can be a prebuild binary (binaries only, you still need the SVN checkout) from http://jeremy.cowgar.com/eubins/ (.tar.gz = Linux, .zip = Windows, eu40osx.tar.gz's = OS X).