Exhibit 10.51

EXTENSION AGREEMENT

This EXTENSION AGREEMENT (the “Extension Agreement”), is entered into as of
August 18, 2015 (the “Amendment Date”), by and between AUTHENTIDATE HOLDING
CORP. (the “Company”) and IAN C. BONNET (the “Executive”).

RECITALS:

WHEREAS, the Company and the Executive entered into an Employment Agreement
dated as of February 18, 2015 (the “Employment Agreement”), under which the
Executive is currently employed as the Chief Executive Officer and President of
the Company;

WHEREAS, the term of the Employment Agreement expires August 18, 2015 and the
Company and the Executive wish to extend the term of the Employment Agreement
for a period ending on September 18, 2015.

NOW, THEREFORE, in consideration of the foregoing and the mutual undertakings
contained in this Extension Agreement, the parties agree as follows:

1. Extension of Term. The Company and the Executive hereby agree that as of the
Amendment Date, the first sentence of Section 9 of the Employment Agreement is
hereby amended and restated to read as follows: “The initial term of this
Agreement is for seven (7) months from the Start Date (the “Expiration Date”),
unless sooner terminated upon the death of the Employee, or as otherwise
provided herein.” Accordingly, the Company and the Executive hereby agree that
from and after the Amendment Date, the term “Expiration Date”, as used in the
Employment Agreement, shall mean and be September 18, 2015. From and after the
Amendment Date, all references in the Employment Agreement to the “term” or
“duration” of the Employment Agreement shall give effect to this Extension
Agreement.

2. Modification; Full Force and Effect. Except as expressly modified and
superseded by this Extension Agreement, the terms, representations, warranties,
covenants and other provisions of the Employment Agreement are and shall
continue to be in full force and effect in accordance with their respective
terms until the Expiration Date or any earlier termination of the Employment
Agreement. To the extent there are any inconsistencies or ambiguities between
the specific subject matter of this Extension Agreement and the Employment
Agreement, as amended to date, the terms of this Extension Agreement shall
control.

3. References to the Employment Agreement. After the date hereof (i) the
applicable portions of this Extension Agreement shall be a part of the
Employment Agreement, and (ii) all references in the Employment Agreement to
“this Employment Agreement,” “this Agreement” and phrases of similar import,
shall give effect to this Extension Agreement.

4. Miscellaneous. This Extension Agreement shall be governed and construed in
accordance with the laws of the State of New Jersey, without reference to its
conflict of laws rules. Capitalized terms used but not defined herein shall have
the meanings ascribed to such terms in the Employment Agreement. This Extension
Agreement contains the entire agreement and understanding of the parties with
respect to its subject matter and supersedes all prior arrangements and
understandings between the parties, both written and oral, with respect to its
subject matter. This Extension Agreement may not be amended or modified except
in the manner for an amendment of the Employment Agreement as set forth therein.
The observance of any term of this Extension Agreement may be waived (either
generally or in a particular instance and either retroactively or prospectively)
in the manner set forth in the Employment Agreement and the failure of any party
at any time or times to require performance of any

 

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provision hereof shall in no manner affect the rights at a later time to enforce
the same. No waivers of or exceptions to any term, condition, or provision of
this Extension Agreement, in any one or more instances, shall be deemed to be,
or construed as, a further or continuing waiver of any such term, condition, or
provision. This Extension Agreement shall be binding upon and shall inure to the
benefit of and be binding upon the parties hereto and their respective
successors and assigns. This Extension Agreement may be executed in
counterparts, each of which shall be deemed an original, but all of which shall
constitute one and the same instrument. Executed counterparts may be delivered
via facsimile or other means of electronic transmission.

Remainder of page intentionally left blank; signature page follows.

 

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IN WITNESS WHEREOF, the Executive has individually signed this Extension
Agreement, and the Company has caused this Extension Agreement to be signed by
its authorized representive, all as of the date first written above.

 

AUTHENTIDATE HOLDING CORP.   EXECUTIVE By:  

/s/ Charles C. Lucas

  By:  

/s/ Ian C. Bonnet

Name:   Charles C. Lucas     Ian C. Bonnet Title:   Chairman of the Board of
Directors    

 

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