The device, with its custom firmware, presents itself as a Hayes modem sitting on the serial port of the host computer. Insofar as a dialup modem can be used to connect to the Internet, this can be. And that would be, I suppose, PPP or SLIP dialup -- which is not very practical or what you're looking for, I think.
The goal of the creator here was to create a modem that "dials" out to the internet.
I was thinking that this had similar features as the plipbox, exept for that this use serial port instead of paralell port, and wifi instead of wired ethernet. And this had the same functionallity as other serial-to-ethernet converters, that enables you to connect to your local network or the internet.
But I guess that for internet, the plipbox might be a better option.