Newsprint and cardboard are generally considered safe for the soil, though glossy prints are not recommended. Soy and water-based inks are used on newsprint. I'm not finding research based specifically on the glue used in cardboard.
Here are articles with more information:
FAQ Cornell University Waste Management System, Composting in Schools, (third question) http://compost.css.cornell.edu/faq.html#newspaper
The Garden Professors, Extension, "Why I don't like cardboard mulch" http://blogs.extension.org/gardenprofessors/2012/06/20/why-i-dont-like-cardboard-mulch/ and "Sheet mulching--benefit or barrier?" http://blogs.extension.org/gardenprofessors/2010/09/16/sheet-mulching-benefit-or-barrier/.
Yes, black newspaper ink is soy-based and may be used as a soil mulch. Cardboard? I don't know, but I have used cardboard mulches and wouldn't hesitate to do so. But I don't have any science to back that up.