The generated source for the Cog VMs is available from the Squeakvm subversion repository:

svn co

Building instructions are in the build directories, e.g. build.macos32x86/HowToBuild

You can find unofficial pre-built VMs for both V3 and Spur format  Squeak and Newspeak images under

You can find bootstrapped Spur images in    Send article as PDF