choosealicense.com/javascripts/clipboard.js

$(document).ready(function() {

  // Backup the clipboard button's original text.
  $(".js-clipboard-button").data('clipboard-prompt', $('.js-clipboard-button').text());

  // Hook up copy to clipboard buttons
  var clip = new ZeroClipboard($(".js-clipboard-button"), {
    moviePath: "../../javascripts/ZeroClipboard.swf"
  });

  clip.on('mouseover', function(client, args) {
    // Restore the clipboard button's original text.
    this.innerText = $(this).data('clipboard-prompt');
  });

  clip.on('complete', function(client, args) {
    this.innerText = 'Copied!';
  });

});