Strictly observant Jews can't have McDonald's hamburgers for two
reasons: (1) they cook pork and dairy products on the same grills as beef,
What pork or diary products do they grill at all??

The sausage and bacon in the breakfast sandwiches, and the cheese
slices on cheeseburgers.

However, many Jews and Moslem are not that observant. But they will not
eat pork. That is a strict taboo.
The Moslem prisoner we help in prison in France draws the line at pork, he won't
touch it. But he does not insist on Halal.

Some Jews or Muslims who are not religiously observant but were brought
up never eating pork often simply don't have a taste for pork and avoid
it.

The commercial creation of a Moslem hamburger fast food is probably more social
than anything, a declaration of being different,

Would a fast food chain aimed at Latin American immigrants to the US be
a social statement and declaration of difference, or simply an effort
to capitalize on a market?

Moslem pride if you wish. I suspect that 70-80% of both the French Moslems and
Jews are not strictly observant

That is probably true. And 95% of French Catholics?

but the Moslems in particular have a statement to make.

Which is understandable, since Muslims are economically and politically
marginalized in France, and many of them feel alienated from the
mainstream of French society.