Apparently this is not true anymore...
Although I have not been able to find the executive order...there may not be one..and I don’t know any federal prisoners personally, it is quite possible and easy to shift the entire diet to kosher and thus appease the Muslims, as they both, Muslims and Jews, derive their diets from the same source.
Kosher food and cooking and eating is unbelievably expensive compared to conventional cooking, or even compared to halal, whose restrictions are quite minimal.
Here’s one explanation:
http://forward.com/news/155363/not-just-jews-eat-kosher-food-in-prison/