I wish to create an AGPLv3 project which uses an underlying framework which is MIT-licensed.
The framework offers some source code which needs to/can be modified to make the framework bend to the users' needs. When I modify those files, can I convert them to AGPLv3 (while keeping required copyright notices of course) or should they stay under the MIT license?
Or am I just overthinking this and a simple notice such as "This project uses the FooBar v1.2.3 framework which is MIT-licensed" in a README would be enough?
EDIT: For clarifications, I'll describe the project structure.
The project and all libraries are written in the PHP language. I have the framework installed via a package manager (Composer), which creates a vendor directory where the framework's "core" is available.
The installation also creates some bootstrapping for me to use (config files, application bootstrap sequence, some baseline MVC pattern goodies). These will be the base of my project.
The things that are installed into the vendor directory are not shipped with the project source but are required for operation and are installable via the package manager. Files and other components are linked from the vendor area by using a simple file
include feature of the language, and are not modified in any part of the project.
Can I convert the bootstrapping code to AGPLv3 while the contents that are living under the vendor directory stay as MIT?
Most PHP frameworks operate on this principle and 99% of projects are done this way. I just want to be sure that I'm legally on the right grounds when licensing the project itself and writing about copyrights.