Is it possible to alter the code of the [Chili plugin](https://code.google.com/archive/p/jquery-chili-js/), which had its latest release on July 2008, and it is licensed under the MIT license, to then license it under GPL?

As far I can see, there is no restriction about the new code being licensed under the same license. Is it really so, or is there a minimum number of changes? 

In my case, I would change the jQuery plugin in normal Javascript code that is executed in a CMS.
This essentially means that, among other things: 

* The code will not use the "ChiliBook" namespace.
* The function will not be invoked as `$($element).chili()`, but as `GlobalObject.ChiliHighlighter.process($jquery_element)`, where "GlobalObject" is a JavaScript object used from the CMS.
* The code will allow other modules to alter the `GlobalObject.ChiliHighlighter` object to add functions that are optionally called from `GlobalObject.ChiliHighlighter.process()` when they are defined.

As alternative, as the repository I am using allows me to include code not licensed under GPL 2 or higher license when the code is not maintained anymore, could the plugin be considered not maintained anymore, as its last version was released three years ago?