The glowworm does not have a backlight, and neither do any of the e-ink Kindles nor any other e-ink device that's currently being sold, as far as I know.
The glowworm has a bank of lights under the top bezel that shine down, and those are well implemented.
The only prior self-illuminated e-ink screen was in a Sony from a couple of years ago, and people hated it - the illumination was very uneven and the battery drain was apparently fierce.
You actually can't have a backlight on an eink screen, since the screen is opaque. This is part of why Amazon recently bought a company that manufactures ribbon lighting, so the next generation of eink kindles will also have onboard illumination.
The Mirasol technology displays are interesting - they are somewhat like e-ink in that they are highly readable in full light, but they are backlit for indoor reading. The battery life on that technology is better than on LCD screens but not as good as on e-ink, and the first reader using one commercially was released in Korea last year to generally mixed reviews. (These are color displays, but the colors are nowhere near as rich as on an LCD and refresh rate is also not yet up to par.)