Moonlighting is working in addition to a regular full-time job, usually after-hours. Use this tag as a generic "Freelancing while employed" tag.

moonlighting: verb /ˈmuːnlaɪtɪŋ/

To work at an additional job after one's regular, full-time employment, as at night.

(Source: Collin's English Dictionary Complete & Unabridged 10th Edition <dictionary.reference.com>, accessed 5th March 2014)

Moonlighting is freelancing done in addition to a regular full-time job, with or without telling your (full-time) employer, and usually after-hours.

Moonlighting generally occurs when an employer is under-paying someone, or their circumstances change and they have to work extra hours.

It can also occur if a person wants to develop their skills (or a different set of skills) away from their company while maintaining a steady income.

Use this tag as a generic "Freelancing while employed" tag.