The reason for that is that Quebec is much more protective of the French language so they will always translate everything, even the names.

There is a law in Quebec called “loi 101” which aims to protect French language. Among other things, it forces movie titles to be translated.

Black Pearl being a “translatable” name I guess it would fall under this law. (Not 100% sure about that, might also be for marketing.)

In France, however, names are usually kept in the original language. Also, in France people have integrated a lot of English words into the spoken language.

So sometimes, for marketing reasons, a movie title will be translated into another English title but something that most people will understand. A notable example would be The Hangover having been translated into Very bad trip.

As for the “noire” not being capitalized, I guess it’s because noire is an adjective and in French, when using simplified rules for writing titles, only nouns are capitalized.*

*For general rules, special cases etc… please refer to this page.

Canadian French titles are, I think legally , fully translated, most of the time very literally. Quebec is actually much more protective of French than France itself. I guess being surrounded by English makes you more enclined to protect your language by laws… Some French Canadians out there might provide more insight on the matter I guess.(EDIT: cfr edit here below, it is indeed legal and from my research the reasons/goals of it are exactly that, protection of French language)
In other French-speaking countries, titles are “adapted” rather than translated. There are also examples of English titles being adapted but still in English.

About you extra question, “noire” isn’t capitalized because French is much more strict/complicated than English on capitalization and in this case, “noire” being an adjective isn’t supposed to be capitalized in French. “Perle” is capitalized because “Perle noire” is a proper name and proper names are supposed to be capitalized.

EDIT:

I did some research on Loi 101 mentionned by @seg-s in his answer. It was promulgated in August 1977 in order to protect French language. It seems it gets stricter and stricter broader and broader over years and it causes a lot of discussions.

I also found, for reference, an article with some examples of translations. The ones I personally find really “funny” are :

• Trainspotting vs. Ferrovipathes
• Frissons vs. Scream
• Fiction Pulpeuse vs. Pulp Fiction
• Rapides et dangereux vs. Fast & Furious
• Danse lascive vs. Dirty Dancing
• Les bagnoles vs. Cars

Industry related, examples

• The dubbing and translation related industry has country specific
  ramifications; there is competition for the translation rights to
  American productions; sometimes France dubs for the world, sometimes
  Quebec does, sometimes each go their own way etc.
• The majority of English movies distributed in France had their title translated to French in 2010 (this is one source); there is nothing specific to Quebec in that respect.¹
• Some of the industry traditions vary depending on the market; in France
  you will have renaming of some English titles per se (see this
  insightful article ²). A renaming can also occur for
  various reasons from one variety of the French language to another –
  for instance the same article lists Lance et Compte (1987)
  from Quebec, renamed Cogne et gagne in France³. Obviously with
  speech you’re trying to cater to what is familiar within
  the target dialect or sociolect to create an immersive experience;
  there are possibly as many differences between markets as there are
  differences in France itself, and between France and other countries in the Francophonie in
  terms of what the viewership considers usual and natural spoken
  French; and those differences can be considerably greater than with the written language.

Observations about the Black Pearl

• The stance on the integral borrowing of casual words from the English language might differ between France and Quebec and this might steer the speaker’s choice.⁴ One can’t say for certain what the translators had in mind when translating here, but we can expect a translator to be first and foremost a speaker. From my point of view, in my world, English is not a prestige variety for the
  French language; there is no context where it is “authentic” in written form except when one writes in English. This is not a movie where people use English car terminology because they’re dealing with English speaking suppliers etc. Furthermore, English
  pronunciation within a sentence in French is often incompatible with
  French phonetics; constantly having to “switch” from French to a
  standard English pronunciation in the middle of a sentence, then back
  again, is disturbing and tiresome, especially to say basic words which
  already exist in the language. Parsing English words within French text
  also hinders readability as one naturally expects French when they read in French; this is not speech this is written French text in a title. Finally, if the Black Pearl is not
  some exotic string of words in English then why should it be so in
  French?

• On the other hand, as someone mentioned, the underlying generic
  is the galleon here (galion, n. m., a type of gallère, n. f.).
  The interest lies in how you’re going to leverage grammatical gender
  in the context of a boat name with varying underlying generics. Gender has an impact on how this sounds.
  Bateau, vaisseau, navire are masculine; goélette, frégate and such are feminine etc.. Then again, it is possible to use the masculine irrespective of the gender of perle (n. f.) for instance, and
  the French Marine nationale does so, which is consistent with modern trends in the field. The Le bon usage (Grevisse and
  Goosse, ed. Duculot) discusses boat names at §475; you basically
  have an equal set of examples where authors use an article which
  reflects the gender of the underlying generic, or not. The most well
  known case is undeniably that of Verne’s le Nautilus, which has both the
  masculine article and the capitalized N. But it’s a simpler case also involving a sous-marin (n. m.) and Nautilus doesn’t have a feminine ending. I did not watch the movie you speak of and don’t have access to possibly different versions of the dialog to see if they refer to any underlying type of boat or generally how they would deal with using Perle noire⁵.

• Generally proper nouns start with a capital letter and LBU at §99a)2
  indeed refers to boats sometimes being equated with such nouns. If
  a noun, especially a nickname, is made out of many words, all of them
  would usually start with a capital letter. The current French Navy ships include La Grande Hermine and Belle Poule, but the adjective comes first and this makes a difference as someone explained. I can’t come to terms with this complexity and with applying the rules to the boat name form found in this case. More generally, one can look into the topic of capital letters to add significance and how generally capital letters should only be used if required. The subject requires a much more careful study (see specific uses).

_Notes

_{1. You would think it’s common business sense to present your product in French when the overwhelming majority of your customers happen to be French speaking. In that respect the Charter of the French Language simply makes sure you have comparable results to what ends up happening in France in a different but comparable scenario. History’s lessons are remembered; money talks louder than good intentions so you need laws to strike a balance against carelessness or ignorance; and a balance has been struck. But this is really about the idea of inscriptions on products for sale i.e. labels, not content; there’s no guideline for translating a movie title, and this is not about the name of a business. La Malédiction du Black Pearl is a title in French containing two English words; I don’t see what relevance the law (section 51) has here and why it was brought up (in the answers). One should also note the Charter doesn’t require a movie to be dubbed to French, and in that case no French material or label is required (see q. 29, 30 here). Otherwise according to Wikipedia it seems New-Brunswick went along with the Quebec version of the cinémafrancequébecrégionalismestraduction}