Quoting http://sourceforge.net/forum/message.php?msg_id=5706177 for your kind attention:
o_OYes, LZMA SDK is in the public domain now.
Do you have any problems with "public domain" status?
The main reason of new "license" was the wish to increase usage. For example, FreeBSD people don't like LGPL code.
I'm also thinking about "public domian" status for 7-Zip. But now I don't see any big advantages of that. What do you think?