Interesting study. I wish there was more like this.
Here's my take. Their CFS mouse model seems to cover what would otherwise be induced by EBV and other pathogens. But it isn't sustainable CFS that is induced by Poly I:C. It's a reversible CFS condition without the maintaining background pathology. Their proposed medicine at least improves recovery. I would have to look at the drug's mechanisms of action to form an opinion if it could also help with chronic CFS/ME.
I would change their mouse model in that I would use the drug simultaneously with a strong immune suppressant and an EBV mutant taken from a CFS/ME patient. This could actually induce chronic CFS/ME. But I'm not sure if it could work with mice because they are the original hosts of EBV, so they might have evolutionally acquired resistance to developing the chronic form of the condition. The reason for this might be that their immune system handles EBV so well that CFS/ME couldn't be triggered. And that's why Poly I:C and immune suppression could help.
In the coming week or so, I will write a more sophisticated explanation of my thymus theory and how other common hypotheses and this mouse model fit into it.