It seems the fix was removed in 8642ce5. lib/jasmine/config.rb doesn't require json on HEAD and when I bundle against HEAD I get the above error.
If I add require 'json' after require 'erb' in lib/jasmine/config.rb then the error goes away. All the tests pass or are pending.
Re-fix issue #70 - uninitialized constant Jasmine::SeleniumDriver::JSON
Hmm, fair enough, I don't see any reason why require 'json' should've been removed (probably unintentional, as tests still passed on my machine), we'll re-add for now ... Thanks for tracking this down, hoping we're not just moving the problem around. More refactors are coming in soon that should help reduce the require guessing game.