As evidenced below, sharing works in the Sigma Repository is not considered prior publication.
Most journals do not consider the dissemination of gray literature to be prior publication. What is gray literature? Posters, oral presentation slides, theses, dissertations, and reports are examples of gray literature. In other words, gray literature is what you submit to the Sigma Repository.
Below is a checklist provided by Elsevier to their journal editors. Elsevier is a leading publisher of some of the most well-respected journals in the world. The list is an accurate example of what many editors look at when deciding if a manuscript has been previously published.
The first column in the table shows a publisher's criteria for determining if a disseminated work has been published versus shared. The middle column reflects the Sigma Repository's policy related to the criteria. The third column answers the critical question, "Is an item posted in the Sigma Repository considered published and will it trigger editors to deny a manuscript submission based on the work posted in the repository?"
View the original article on Elsevier's website: https://www.elsevier.com/connect/editors-update/ive-seen-this-somewhere-before!-what-counts-as-prior-publication
Prior Publication Criteria
Copyright remains vested in the submitting author. The Sigma Repository requires a non-exclusive license, only.
Items in the Sigma Repository are assigned permanent handles for location and preservation only.
The Sigma Repository does not have an ISSN and is not a serial publication.
The Sigma Repository does not have a double-blind peer review process.
Posting material in the Sigma Repository is not equivalent to journal articles.
Nurses consider gray literature as valuable/ trusted information.
Due to the nature of the submissions, authors make significant revisions and updates to the work posted in the S.R. prior to publication in a journal.