One reason to prefer textual UIs is that you can use them from any computer anywhere fast (no slow video VNC). Also, if you are already using a terminal, then improving that experience is nice. There is a big enough market there for this company.
However, I'm not sure what a "proper" GUI is. Terminals have a widely used open standard. These protocols are more standard and interoperable than any GUI framework, and they are supported on every system. Once you add video in there, close a few more gaps, I think competing with the browser, or bringing the full computer experience to the terminal is reasonable.
Obviously if terminals add something like video, it's "copying" rendering pipelines from "proper" GUIs, but making the terminal experience better, which could also be viewed as bringing UNIX zen to GUIs, if it makes it big, you'll love it too! <3