Copy from the actual license file in the package:

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xlsReadWritePro
Copyright (C) 2006 - 2010, Hans-Peter Suter, Treetron, Switzerland.
All rights reserved.

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xlsReadWritePro end-user license agreement (EULA)
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This agreement ("EULA") is a legal agreement between you (either an individual
or a single entity) and the author of the software identified above.
By installing this software, you indicate your acceptance of this agreement.

GRANT OF LICENSE.
  1. Unlicensed version - Evaluation
     You may use the software without charge for thirty (30) days from the day
     you install the software. After the evaluation period you must pay the
     license fee to continue to use the software.

  2. Licensed version
     There are 3 standard licenses issued for xlsReadWritePro:

     - A SINGLE USER license. The user purchases a license for the use of
       xlsReadWritePro by a single user. You may make copies to other computers,
       but a license for the software may not be shared by alternating use of
       the software between different users.

     - A COMPANY/ACADEMIC WIDE license. The number of users is unlimited
       as long as they are at the same physical location (site) and belong
       to the same organisation (company/campus/university). Exceptions from
       the physical location restriction possible upon separate arrangement.

     - A lowcost NON-COMMERCIAL license. Can be used on one or two specified
       computers. The license is bound to the system by a HardwareHashID.

  3. Custom builds and redistribution with user R applications are
     subject to a separate license agreement. As a pointer: so far the
     company/academic license has been accepted for redistribution/bundling.

  4. Source code
     While the package (DLL) normally is distributed in binary form, we are
     ready to grant source code access for company/academic wide licensees
     by signing a non-disclosure agreement. The exacact conditions have not
     yet been determined but we are happy to listen to your needs and find
     a satisfying solution.

DISTRIBUTION.
  You are hereby licensed to make copies of the software as you wish; give exact
  copies of the original software to anyone; and distribute the software in its
  unmodified form via electronic means (Internet, BBS's, Shareware distribution
  libraries, CD-ROMs, etc.). You may charge a distribution fee for the package,
  but you must not represent in any way that you are selling the software itself.
  Your distribution of the software will not entitle you to any compensation from
  the author. You must distribute a copy of this EULA with any copy of the
  software and anyone to whom you distribute the software is subject to this EULA.

STATEMENT REGARDING R.
  The package is a non-free non-standard package (from an R point of view). It is
  dynamically loaded into R and interfaces R only through LGPL'ed API header files.
  According to the announcement in 2001 such code is allowed to be distributed under
  licenses other than GPL. See also statements in the file "R_Home/Doc/COPYRIGHTS".

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS' AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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