many times people have been asking where the default theme here on SimpleMachines.org can be downloaded. To save hassle and for everyone to know, read on:
The current theme on SimpleMachines.org is just the Core theme that was released in the RC stages of 1.1. The difference is that here we have added a new layer and new colours.
Unfortunately at this time it is not for download and it has not been decided if it will be included in the new SMF 2.0 when it is released.
I hope this clears some minds.