It's not a DOS shareware game.
As for your question, the shareware scene did change with the rise of prominence of Windows, but it didn't vanish altogether. There are many modern Windows shareware games that use the unlock code model - you download the full game but some of the features are locked until you purchase a code from the developers.
Spiderweb Software,
StarWraith 3D Games and many other developers all work like that.
That said, the guy who looked for the game said that
maybe the demo he had offered an option to enter an unlock code to convert it into the full version.