how is this a flip flop hub?
 

if there is nothing on the other side?

http://philadelphia.craigslist.org/bik/78264649.html

Can't tell for sure, but it looks like there are threads on the other side of the hub, making it a flip/flop.

flipflop means the hub is capable of carrying a cog or freewheel on both sides, not that it has a cog or freewheel on both sides.
a freewheel hub with no freewheel is still a freewheel hub.

do you think its an elusive double free flip flop or did he put his freewheel on the fixed side of the hub?

That's a mountain hub, nothing elusive about a double-free mountain hub.

so if that's a mountain hub does it have 135 spacing? I haven't worked with the surlies, how flexible are they with regards to axle spacing?

ha
yo alex