Did this really happen?
The Paris Mosque is a real place that really was involved with both Algerian immigrants and the French Resistance. Its director Si Khaddour Ben Ghabrit really was awarded the Medal of the Resistance in 1947. The singer musician Salim Halali really did talk frequently about being saved by the Paris Mosque. The rest are "imagined" "composites"; most likely correct in spirit, but not aligned with any particualr individual.
For some evidence for the non-professional historian, a simple Google turned up http://parismosque.blogspot.com/p/main-characters.html . (Of course there's not lots and lots of evidence, because folks tend to not leave written records of their "illegal" activities.)
The Paris Mosque's main focus was Algerian immigrants - both Muslim and Jewish. It seems that it helped save only a few non-Algerian Jews, and all those were children.
The film shows that the immigrants were very poor, tended to live together in what amounted to ghettos, and weren't treated very well by the factories where they worked (hence the union activity). But much of this faded into the background for me anyway, until the "Extras" on the DVD called it out more explicitly. What the film doesn't show is that the poverty, separate living quarters (HLMs nowadays), and poor employment treatment continued. The film also shows explicitly that the immigrants' involvement with the French Resistance was motivated in large part by the idea Algeria would gain its independence too at the end of WWII. What the film doesn't show is that Algeria did _not_ get its independence as part of WWII; in fact the colonial mistreatment of Algeria by France continued for several more decades.
To dramatically oversimplify: although the Algerians weren't treated very well by the French either before or during or after WWII, the non-Frenchmen in the Paris Mosque did a pretty fair job of helping their fellow countrymen. In the process, the Paris Mosque also became a center of the French Resistance.
I'd fault the film for two things: One, making it too easy to misread as "typical" its portrayal of something unusual that centered elsewhere. And two, not saying anything at all about the aftermath of WWII.
I find the "conventional wisdom" about "history" to often be slanted or partially blind, and so am pleased whenever shining light into a previously dark corner provides a chance to "revise" the picture into something fuller and more nuanced.