It's an interesting thought, but according to the article, it's not even clear that the fungus is absorbing radiation or befitting from radiation. Actual photosynthesis-via-radiation hasn't been demonstrated; it might simply be taking advantage of the absence of other species due to high radiation, or the radiation is triggering a stress response.

Beyond that, I'm not sure this fungus would have a better protection-per-ton rating than, say, water (which is an astoundingly good radiation shield). But, it might point us towards ways of developing plants which are radiation-tolerant, theoretically opening a path to growing food in orbital or lunar-surface environments.