Why are the checkboxes different on different devices? Why is there a difference in the look of the checkboxes between this device and this Samsung device?

Is this affected by the launcher, in which case the reason is clear?
Theming is independent of the launcher, although both may be considered part of the UI; for example, the TouchWiz launcher and theme are elements of Samsung's TouchWiz UI.

My Samsung Vibrant is running a custom ROM called Bionix, and they've re-themed the device so my checkboxes look like this (perhaps the only thing I dislike about the ROM):