Just a heads up, this did build for a colleague on windows, but i ran into a long series of problems when building with a clean install of node using apt-get on ubuntu wily. Note that the recommended ppa is not currently available for wily, so i first used the default distro.

** So quite possibly not an issue with the mosaico script. **

...
Running "combineKOTemplates:main" (combineKOTemplates) task
Running "browserify:debug" (browserify) task
Warning: watch ENOSPC Use --force to continue.
Aborted due to warnings.

/mosaico$ grunt
Loading "phantom-thumbnailer-editor.js" tasks...ERROR

TypeError: undefined is not a function

And quite a few others.