It was to be an experiment in solar powered robots that would use the spring as energy storage instead of a battery.
Never built it; this has me thinking about it again, tho.
Providing the gas pressure however is an issue. You can use solid CO2 recharge (drop in some dry ice, seal, and warm) but for the challenge it had to go a looooong way. And that would require a fuel, a generator, and a compressor. Weight went up, survivability went down, and some early tests on what was essentially a pogo stick pointed that it wasn't practical at those mass levels.
Gliding would have been an interesting choice. With something light like a parafoil wing even more so. If I dig up my notes I'll put up something on my web site about it.
It's funny you mention that. I went to grad school with the guy who created the jumping robot. His PhD research was in creating artificial Gecko footpads for robots.
[1] http://northdesignlabs.com/?page_id=12 [2] http://northdesignlabs.com/?p=38 [3] http://www.youtube.com/watch?v=ISznqY3kESI
Funny story, I designed a robot based on the hopping principle for the first DARPA challenge (the one where you were in the desert trying to go from Barstow to Las Vegas) except that we ran into issues with the ground being too soft in places to reliably jump. And the fact that we had an on board compressor which both weighed too much and took too long to recharge the jump tanks, but other than that :-)
[1] https://en.wikipedia.org/wiki/Van_der_Waals_force