How can you tell? Did you work on it for a few months or you can just browse the SVN and notice it's well designed? I look and all I see at first is indentation style and directory organization.
If all you noticed from seriously looking through the source is that it is well indented and well organized, you're probably not an experienced enough C++ programmer to evaluate the merits (no offense intended).
One probably couldn't by merely looking at it. Reading it with the specific intent to understand it, on the other hand, can make design intent pretty clear. (One would hope that the structure of the program is at least homomorphic to the intended design, if not isomorphic.)
If all you noticed from seriously looking through the source is that it is well indented and well organized, you're probably not an experienced enough C++ programmer to evaluate the merits (no offense intended).