if (MSB not set)
Bit# 1 T2A upgrade, enables chatbutton
Bit# 2 enables LBR update. (of course LBR installation is required)(plays MP3 instead of midis, 2D LBR client shows new LBR monsters,…)
if (MSB set)
Bit# 3 T2A upgrade, enables chatbutton
Bit# 4 enables LBR update
Bit#5 enables AOS update (Aos monsters/map (AOS installation required for that) , AOS skills/necro/paladin/fight book stuff – works for ALL clients 4.0 and above)

Bit#6 enables 6th character slot
Bit#7 enables SE features
bit#8 enables ML features
bit#9 enables 8th age
bit#10 enables 9th age
bit#11 enables 7th character slot
bit#12 enables 10th age KR stuff

This was already part of the online packetlist. I edited these infos about a month ago.
You'll find it here:

http://docs.polserver.com/packets/index.php?Packet=0xB9