I think the only part of that command that uses network access is installing gems. Does that match what you're seeing, does it mention rubygems or bundler at the point it's timing out?
The rubygems server seems to be flakey now and then for certain people, I've had that experience too. Hopefully it is temporary, and if you try a couple hours later it won't happen again?
There's not really any way around using bundler to install Umlaut's gem dependencies as a part of installing Umlaut. If you continue to have problems, we could try reporting the problem to the rubygems team. Sorry for the inconvenience.
Jonathan