... I hope you're kidding. Don't reinvent the wheel - if someone else has already written the code then there's no reason to re-write it. That's a huge waste of man hours.
Instead you should package all dependencies in such a way that they can be retrieved without requiring the other guy to still be offering it. Yes, that means a snapshot of the version you rely of should be in your repository because you also can't guarantee that a given version will be available as long as your own project is.