After reports of MSN China’s official native Symbian 9.1 Windows Live Messenger client becoming a trial version, Darla has spotted a Symbian Signed version of the instant messaging client available for free from Nokia China and Nokia Hong Kong.
This version is compatible with any Nokia S60 3rd Edition mobile device.

Alternatives include:

1) PPC Hier’s native Symbian 9.1 S60 client
2) Java based eMSN client (for non Symbian S60 phones also)

Direct download here