Most native speakers of English neither know about nor care about the specific grammar of restrictive and non-restrictive clauses. Language is used to convey information, and any clause may convey relevant, useful, and interesting information, even if it is set off by commas. For example:
Simon Baxter, who is a deep-sea fisherman, is training to be a lion tamer.
The ostensibly non-restrictive clause "who is a deep-sea fisherman" is not critical to the sentence, but the writer would not have included it if it wasn't relevant to the overall point of the sentence (that Simon is switching from one dangerous job to another dangerous job). You can't remove this clause without taking away meaningful information.
So, the real question in your example is whether the phrase "where it opened to great critical and commercial success" is critical information. If you think the main point of the sentence is that the movie was released at Christmas, then its commercial success is interesting but non-essential, and the clause can be called "non-restrictive". If you think the main point is the movie's commercial success, then the clause is essential and can be called "restrictive".
The use of the comma doesn't do anything here. It all depends on your opinion of the writer's intent -- and, in the end, whether we call it "restrictive" or "non-restrictive" is of interest only to professional linguists.