TL,DR: no, there's no compelling reason for the title to be a question (rather the opposite in fact).
I recommend reading the FAQ How do I write a good title?, especially its accepted, highest-scoring answer which is based on scientific research. The salient points are:
Make the topic stand out.
Keep it short.
Lead with the most important words.
The operating system should be included in the title if it's an important requirement. It often is.
It is not recommended to remove the name of the language on Stack Overflow! I think you're confusing this with the recommendation not to include language names as “tags” in titles. That is:
“How do I frobnicate a widget in C?” is a good title
“C Frobnicate a ...
I finally found the mSO post regarding it. Yay! (and thanks Shog!).
From this answer by Robert Harvey (an SO mod):
Requiring a complete, grammatically correct question in the title forces the OP to think about these things when they post their question. Ergo, I believe that crafting a good question title not only improves the title of the question for all ...
Titles should be complete summaries of the question.
Here's the easy rule:
Cover the tags, and ask yourself if the title conveys enough information. It needs to.
That means two things:
Information in a tag in no way makes it less necessary in a title.
But tags need not be added to a title when they're not needed to convey key information
Tags are for ...
While necessarily we may have more than one answer, a good question dosen't generally poll for them, or ask for something subjective like 'best'. You have a problem - with various requirements and constraints, for which there may be an 'ideal' solution for you. Someone may see it differently. There isn't often a 'best' solution, rather a best compromise, and ...
As Thomas said, a "Alternative to XYZ" title is not a the best way to attract good answers. It eliminates people who don't know the potentially out-of-trend XYZ, and it does not contain any keywords. Of course, most software have many features, for instance you might ask "Alternative to Emacs" because you use Emacs as a customer support suite, while the ...
TL;DR: for you own good.
Indeed, nothing prevents you from writing such a title. However, it may be less likely that you get answers, if you consider the following situation.
You have written "Free alternative to Adobe VoCo". Let's say someone reads this title in the question overview. Since Adobe VoCo is not a mainstream product, even just a demonstration ...
This is automatic, as I believe Chrome titles the tab based on the HTML <title> tag. The engine automatically sticks what it thinks is the most popular tag on a question in that title tag, even though it's not present on the actual title at the top of the question. This is part of the SEO strategy we employed to help climb over the SEO scrapers.
I would argue against question titles.
They make all questions look the same, and force readers to loose time on insignificant words before getting to the point of the title. While it might not sound like a huge problem, it waste a lot of time when browsing long lists of questions (for instance when scrolling the home page or search results). They are also ...
The answer from Gilles in Why do people insist titles actually be a question (I seem to be unable to find a “share” link on the specific answer…) refers to a meta.SO FAQ with a scientifically-based highest-scored answer on titles.
The part interesting here is: Do not copy parts of the question in the title.