Thanks, Shawn. It appears that the KAL Lounge is only open a limited time. There isn't much info on the G16 lounge so I might go with one of the paid lounges as a backup.

Lounge
Lounge name : KAL Lounge
Location : In front of Gate 15, 6th floor
Open Hours : <Summer Season (29 Mar, 2009 ~ 24 Oct, 2009)>
- 09:25 ~ 14:15 (KE604/KE614, Mon/Tue/Thu/Sat)
- 09:25 ~ 16:45 (KE604/KE614, Wed/Fri/Sun)
- 20:25 ~ 00:25 (KE608)
Operated by : Korean Air