The article and the investigation both sound like total BS to me. I'm no big Imus fan by any means, but the left has been after this guy for several years due to the politically incorrect humor on his show; e.g., taking shots at gays, blacks, Ted Kennedy, etc.
The real charges seem to be that Imus spends too much money per child and that he and his family live on the ranch for free. As far as the first goes, his is not the only children's charity like this and Imus made the parameters very clear from the beginning.
As far as second charge goes, yes, he and his wife do manage this working cattle ranch for part of year, supervising kids and employees.
This whole thing is an exercise in harassment.