Original unmodified files from the LZMA SDK are included under libclamav/lzma.
The original lzma.txt license file, a small portion of which is reproduced below,
is available under libclamav/lzma/lzma.txt. 

LICENSE
-------

LZMA SDK is available under any of the following licenses:

1) GNU Lesser General Public License (GNU LGPL)
2) Common Public License (CPL)
3) Simplified license for unmodified code (read SPECIAL EXCEPTION) 
4) Proprietary license 

It means that you can select one of these four options and follow rules of that license.


1,2) GNU LGPL and CPL licenses are pretty similar and both these
licenses are classified as 
 - "Free software licenses" at http://www.gnu.org/ 
 - "OSI-approved" at http://www.opensource.org/


3) SPECIAL EXCEPTION

Igor Pavlov, as the author of this code, expressly permits you 
to statically or dynamically link your code (or bind by name) 
to the files from LZMA SDK without subjecting your linked 
code to the terms of the CPL or GNU LGPL. 
Any modifications or additions to files from LZMA SDK, however, 
are subject to the GNU LGPL or CPL terms.

SPECIAL EXCEPTION allows you to use LZMA SDK in applications with closed code, 
while you keep LZMA SDK code unmodified.


SPECIAL EXCEPTION #2: Igor Pavlov, as the author of this code, expressly permits 
you to use this code under the same terms and conditions contained in the License 
Agreement you have for any previous version of LZMA SDK developed by Igor Pavlov.

SPECIAL EXCEPTION #2 allows owners of proprietary licenses to use latest version 
of LZMA SDK as update for previous versions.


SPECIAL EXCEPTION #3: Igor Pavlov, as the author of this code, expressly permits 
you to use code of the following files: 
BranchTypes.h, LzmaTypes.h, LzmaTest.c, LzmaStateTest.c, LzmaAlone.cpp, 
LzmaAlone.cs, LzmaAlone.java
as public domain code. 


4) Proprietary license

LZMA SDK also can be available under a proprietary license which 
can include:

1) Right to modify code without subjecting modified code to the 
terms of the CPL or GNU LGPL
2) Technical support for code

To request such proprietary license or any additional consultations,
send email message from that page:
http://www.7-zip.org/support.html


You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

You should have received a copy of the Common Public License
along with this library.