Anything that attacks my computer and is reported as such and has a detrimental effect on my computer is a virus in my opinion (see screenshots). I won't be alone in that opinion either and other users will abandon visiting your site too if they get that report too so I think you should reconsider using that JS.
Nevertheless, I looked at the demo and worked out the CSS to change that for you rather than looking at your site.
Use this code...
.g-popupgrid-item-img-wrap {
background-color: transparent;
background-image: none;
}
.g-imagegrid .g-imagegrid-item img {
opacity: 1;
}
To create a custom CSS compatible with Gantry 5 please read this
http://docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
.
Remember to recompile CSS from base outline too.
Regards, Mark.