It's not much smaller, but the output and the potentiometer are much lower. I was basing on that design. I modified it for a request of one member of 3dfx.pl forum. Can be useful for small custom made cases too.
Sure, it's free, but ordering materials for 1-off is more expensive than my proposal. I wanted to build 5-10 at home and then sell them, but it was just too expensive. Nearly £20 for the components per board when making 10 of them and another 20 for the PCB (can drop to about 12 if you use the cheapest Chinese crap with no gold plating at all)