It is from the fan-made Halo game called "Project Contingency" I went to their site and I looked around. I found the first picture of the HUD in HD. Which confirms it as not Halo 5, but Project Contingency.
Picture belongs to the Creators of Project Contingency:
When this fan project releases, I am so going to play it.
UPDATE: I found another screenshot. Again. Credit goes to creators.
Ardent Prayer's post in Halo 5 Leaked Photos Proven to be From Project Contingency was marked as the answer