Short answer, yes and no. Gcc is installed in 3MX-rc3.1 (as is perl, python, ruby and tcl/tk), but i've only included the libc6 header files which is enough for simple 'hello world' type programs (to save space). If you were to download all the required .deb packages from a debian etch mipsel repository you could then extract them to the root of the filesystem and have a fully working development suite on the LLL. You'd need make, automake, autoconf, and libtool for sure, then any -dev packages. Such as x11-dev, gtk-dev, glib-dev, jpeg-dev, png-dev sdl-dev etc etc etc to build anything usefull.
FYI, if you need something as heavy as nautilus, this machine is not for you. Spend $50 more and get an eeepc.
Cheers.