It had to have been on a volunteer/unpaid basis.
If he took money form them while in uniform that could get him sent out the door with a Court-martial.
1. He was on assignment as a Research Fellow so apparently your depiction of the situation is not entirely accurate.
2. Just because an organization was involved, does not automatically follow that everyone in that organization, agrees with a policy position of the same.
He got most his 2nd and 3rd stars, under Obama.
I have no knowledge, and no opinion except what I read in the media, which is obviously without the slightest bias. /s
https://en.wikipedia.org/wiki/H._R._McMaster