It is not so important if you choose something reasonable.
Since you are using an open source license, you probably want another developer to find out that he can actually use your code under the MIT license. This is done by simply searching the license file.
Everything that LICENSE, LICENSE.MD, LICENSE.TXT in the root of the repository can be considered easily accessible. I think you can also assume that if a person does not find the LICENSE file, he will look for something else - say, COPY. You want to prevent conflicting licensing requirements. Do not say in your README that something is licensed under the BSD, but in a separate license file it says that it is MIT.
You may also consider detecting with agents other than humans. npm looks for the license field in package.json and displays this on the package information page in npmjs.org.
The CommonJS specification actually speaks of the "license" field. I know that "license" is also supported by npm, although I use it myself. I also know that npm takes a simple string value for the license field. those. "license":"MIT" working.
license - an array of licenses for which the package is provided. This property is not legally binding and does not necessarily mean that your package is licensed in accordance with the conditions that you define in this property. Each license is a hash with a type property that determines the type of license and the url property that is associated with the actual text. If the license is one of the official open source licenses, the official name of the license or its abbreviation can be disclosed using the type property. If an abbreviation is indicated (in parentheses), the abbreviation should be used.
http://wiki.commonjs.org/wiki/Packages/1.1
In addition, itโs good to know that, in principle, you retain the copyright to everything that you publish. If a license is not indicated, or the (potential) user cannot find the license, he must assume that he does not have ANY license to use your work, except for any fair use provisions in accordance with the copyright laws in the country. See Discussion: https://softwareengineering.stackexchange.com/questions/148146/open-source-code-with-no-license-can-i-fork-it http://www.codinghorror.com/blog/2007 /04/pick-a-license-any-license.html
if the license is altered at all from the template, it will not be considered a valid MIT license, but if something else in the file cancels it?
In fact, it would not be clear that you are making something available under the MIT license, while the actual text of the license says something (slightly) different. However, you absolutely have the right to license your work as you wish (within the law. Some requirements cannot be made - and are invalid).
I think that the biggest risk (if at all) of a small ambiguity in licensing is that a potential user may claim that he had the impression that he had the right to use your work in accordance with the terms of the MIT license, since your license the headline said so. You will have more problems filing a lawsuit against this person in court for any violations if he did not adhere to any additional conditions. He could claim innocence, as it were.
I would say: do not use the name of the installed license (MIT, BSD, GPL, etc.) if you do not want to license these conditions. Or, if you use that name, always say "MIT + MY_REQUIREMENTS" or so. โMITโ simply will not be the right โresumeโ.