An academic points out:

There’s nothing wrong with having a grant from the NIH.
The problem arises because that grant most likely paid for Mr. Gruber’s salary during the summer of 2009. (Only academics are familiar with this, but these government grants typically pay for an academic’s time during the summer months).
So there’s a possibility that Mr. Gruber may have been billing the same hours to both HHS and NIH. Put bluntly, there’s a potential case of double-billing here. And any facts that help discredit Obamacare might be worth pursuing.