Why do we need to be cognizant of Dark Sky Compliance? For one, several jurisdictions have firm levels of light pollution that are allowed on city streets. This makes it imperative that the proper lights are chosen so that only what needs to be lit, is lit. Light pollution can be a safety hazard as well as wasteful. It is estimated roughly 40% of outdoor light is unnecessary and thus falls under the realm of light pollution.
BUG rating does not relate to how safeguarded the light source is to bugs getting within (see IP rating). But rather BUG rating stands for Backlight, Uplight and Glare. Light sources with a BUG rating allow for better understanding of how the light will be emitted from the source.