It never rains, but it pours. Yesterday Samsung posted the Android 4.1 Jelly Bean source code for both new Galaxy Tab models and the AT&T Galaxy Note II. Today they're keeping the open source train rolling with the first available code for the new Galaxy S III Mini, the flagship model's 4-inch brother-from-another-mother. The 4.1 code is available now from Samsung's developer website.
If you're wondering why the GSIII Mini needs separate code from the standard Galaxy S III, remember that it's actually quite a different beast under the hood.