Where to get Evolvotron
...for GNU/Linux and BSD
If someone has already packaged Evolvotron for your distribution, the easiest thing is to use that:
There may be a few .debs for the current Debian/Stable (386, amd64, sparc) and the latest Ubuntu (386) on the SourceForge downloads page. These are built using the Yada packaging helper (strangely unpopular with real Debian developers) and mainly intended to sanity-check build dependencies and the general feasibility of packaging the application. They are provided in the hope they may be useful, but in general the "official" packages for your distro should be preferred.
If you need to build it, download and unpack the source release (gzipped tar file) from Sourceforge and read the README. Assuming you have Qt (with qmake), a correctly set up gcc and the Boost libraries, it should be straightforward to build.
...for the Mac
Forrest Walter has contributed a Mac build of a recent (Qt4) version which can be downloaded from SourceForge. IMPORTANT: Mac users will need to obtain and install a version of the Qt framework on which evolvotron depends, probably from here. NB Qt is NOT the same as QuickTime!
There's also an older Mac port at ATG. Note that you will also need to install the supporting Qt toolkit separately; one is available from the ATG site. (NB Qt is NOT the same as Apple's Quicktime).
evolvotron is also available via the Fink project.
...for legacy systems
I'm not currently aware of any port to win32. However all is not lost if you are unfortunate enough to be stuck with such a system: your hardware can probably be temporarily booted into Linux using the Ubuntu install CD/USB's "Live" mode. This allows you to simply boot up a Linux environment directly from the CD/USB without touching your machine's regular setup or installing anything on your hard drive. Evolvotron should be visible from current Ubuntu release's package manager and installable into the live system for temporary use.