First, I hope this was a good-natured joke; Tom's exploratory project ought not be held to production standards.
That said, this pull request does highlight one DRY opportunity: git submodules [1]. The jQuery+SproutCore integration here could've been two submodule 'links' rather than 24,000 lines of copied .js library code.
As long as the dependencies are on git and the commit 'version' you're linking to doesn't disappear, you're good.
I've used submodules quite often, but in my deployment setup the checked-out/built version ends up stored, since I keep the deployed tree in its own branch[1].
As long as you link to the version you link to, it won't disappear in your local repo, and you can re-publish that as necessary :)
That said, this pull request does highlight one DRY opportunity: git submodules [1]. The jQuery+SproutCore integration here could've been two submodule 'links' rather than 24,000 lines of copied .js library code.
As long as the dependencies are on git and the commit 'version' you're linking to doesn't disappear, you're good.
[1] http://book.git-scm.com/5_submodules.html