It was publically released at Betanews. I downloaded it from there just 10 min's ago.
There where also 5-6 usercomments about it.
The text also said that Microsoft had released it as a Public Beta.
EDIT: Luckily I saved some screenshots and the downloadlink directly from Betanews and also from Microsoft.
Perhaps they made a mistake and removed it. But when I downloaded it, it was legal according to my screenshots.
The link from Betanews looked like this (Censored by me to protect the innocent)
hxxp://fileforum.betanews.com/sendfile/xxxxxxxxx/..._MSN_Messenger.exe
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