LZMA SDK is written and placed in the public domain by Igor Pavlov.

Some code in LZMA SDK is based on public domain code from another developers:
  1) PPMd var.H (2001): Dmitry Shkarin
  2) SHA-256: Wei Dai (Crypto++ library)

You can copy, modify, distribute and perform LZMA SDK code, even for commercial purposes,
all without asking permission.

LZMA SDK code is compatible with open source licenses, for example, you can 
include it to GNU GPL or GNU LGPL code.