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, distributed and perform LZMA SDK code, even for commerical purpose,
all without asking permission.

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