Roboctl: Available as an official FreeBSD port and MacPort.
A Gentoo port is also available, but check to make sure it's the
latest version.
For other systems, the source code can be obtained at
http://personalpages.tds.net/~jwbacon/vex.html
A programming editor: APE (Another Programmer's Editor) has
built-in support for programming the Vex using SDCC and roboctl
under FreeBSD, Mac OS X, Linux, and Cygwin.
APE is also available at
http://personalpages.tds.net/~jwbacon/vex.html.
Note
Included with the library are "robotize" scripts to automatically
install SDCC, roboctl, and APE on
FreeBSD, Mac OS X, Debian, and Cygwin systems.