Canon's overview for lenses with EF-S mounts does not use the descripton DC. The reason for why several third-party resellers use this description remains unclear to me
This list on Wikipedia suggests that the DC version of the lense is the basically the same, but without image stabilization.
Block diagrams
(source: Canon)
EF-S18-55mm f/3.5-5.6 III
EF-S 18-55mm f/3.5-5.6 IS II
Description
(source: Canon)
EF-S18-55mm f/3.5-5.6 III
The Canon EF-S18-55mm f/3.5-5.6 III is a lightweight, compact standard zoom lens specifically for cameras that take EF-S lenses.
Featuring a high-precision aspherical lens element, the lens
compensates for chromatic aberrations that can occur while zooming to
deliver high-resolution, high-contrast imaging performance. Through
optimized lens positioning and coatings, the model greatly minimizes
the flare and ghosting commonly associated with digital camera
photography. It is a worthy successor to the EF-S18-55mm f/3.5-5.6 II
and features a revamped external design.
EF-S 18-55mm f/3.5-5.6 IS II
The new Canon EF-S18-55mm f/3.5-5.6 IS II inherits the highly regarded
optical design utilized in its predecessor, the EF-S18-55mm f/3.5-5.6
IS, released in September 2007. Featuring a high-precision aspherical
lens element, the lens compensates for chromatic aberrations that can
occur while zooming to deliver high-resolution, high-contrast imaging
performance. Through optimized lens positioning and coatings, the
model greatly minimizes the flare and ghosting commonly associated
with digital camera photography. Furthermore, the EF-S18-55mm
f/3.5-5.6 IS II includes an optimized control algorithm that has been
aligned with the Image Stabilizer structure and characteristics,
achieving image stabilization equivalent to approximately four
shutter-speed stops.
Based on a shutter speed of "1/(focal length x 1.6)" seconds, considered the limit to prevent hand shake during hand-held
photography.