I was under the impression that by "text mode" he meant anything but X-Windows. Linux has an API called SVGAlib that is used almost universally for non-X-Windows graphics. SDL, the wrapper library that DOSBox uses for graphics, supports SVGAlib (I think), so DOSBox should too. I wouldn't know how to make it work though.
There's also an extension to SVGAlib that makes it use text modes as graphical modes (I remember someone released ttyquake, a port of Quake 1 that runs in text mode), but that's another story and it wouldn't translate the DOSBox text modes to Linux text modes.