Q. How do I know if it is OK for me to share my thesis/dissertation in DASH?

I will step through the important details that you (as the author) need to think about.

First some Vocabulary and Definition of Terms:
1. Most publishers do not allow authors to share the published article. (I am ignoring some exceptions to this rule for purposes of this example) 

Let's call this version "The Publisher’s Article that was authored by you". This file is the PDF Article that you find at the Journal’s web page.

2. The thing that you will be sharing in DASH is a manuscript that was written for the Thesis/Scholarly_Project 

Let's call this version "The Author’s Manuscript". It is the DOC file that most probably looks like your last version of the project as it was written in WORD

Note: The Thesis/Scholarly_Project must contain the “Author’s Manuscript” (the thing that looks like a WORD DOC) 

Now here is the important part:

[ At the time when you are uploading your thesis into DASH ]

The “Author’s Manuscript” has only one of these 2 flavors:
A:  The "Author’s Manuscript” HAS NEVER been accepted for publication by some peer-reviewed journal 
(This we call * Author’s Manuscript: PREPRINT)

OR

B:  The “Authors Manuscript” HAS been accepted for publication by some peer-reviewed journal
(This we call * Author’s Manuscript: POSTPRINT)

NOW Here is the key Question:

Do you have (A) or (B) in the thesis that will be uploaded into Harvard’s DASH (ETD) system?

Every student uploading something into DASH will have either a PREPRINT or a POSTPRINT for any given chapter of the thesis.

These two distinctions are important, because publishers have expectations for how they can be shared by authors.

For example,  Elsevier (and most publishers) have perfectly friendly sharing policies with regard to PREPRINTS and POSTPRINTS
https://www.elsevier.com/about/our-business/policies/sharing

In this Elsevier example… PREPRINT can be shared “anytime or anywhere”…and the POSTPRINT can be share “after the embargo period.” 

Whenever you have a POSTPRINT contained in your thesis, you will need to think about the embargo period that the publisher has requested of you. Generally this period is 12 months, but it can vary. (Rarely is it ever more than 12)

During the uploading process into the ETD / DASH system, you will have the opportunity to select the appropriate embargo period.