We were looking at these examples and widget01.png isn't opening for us so can you re-post that? In general, is the issue that...
the script is adding two duplicate copies of the corner classes and should check if a corner class already exists on an element and only add a new class is there isn't one
- or -
that you want programmatic control to specify where corner classes are applied (ex. "don't round the top two corners" or "don't round any corners" on the tab header)
The first scenario is relatively easy to do and it a good idea anyway, the second seems like it could be very complex.
In your example image, if you didn't want the tab header to be rounded the simplest way to fix this is to create an override stylesheet that you reference after the theme css. In this, just override the corner radius to 0 for the ui-tabs-nav element.
_t