For me the most important defining characteristic of a framework is inversion of control. With a framework high level control flow is dictated by the framework itself. It follows from this that using two different frameworks can be challenging.
An abstraction layer over a database is not necessarily a framework, it can be just a library. I'm not familiar enough with specific ORMs to comment on those.
A programming language is interesting to look at from this point of view. While sure, you need to use the programming language's features to implement control flow, it typically doesn't actually dictate a high-level control flow itself. There are probably languages where this is not completely true.
By this definition, though, which does seem to be the one used by the article, both Flask and Sinatra are frameworks. Which I don't necessarily disagree with, but there are tons of people here in the comments arguing the opposite.
For that matter, it seems to me that CGI would be a framework in this sense - the high level control flow is that you are called by the web server, run, take input from environment variables, output an HTTP response, and exit. Not fundamentally different from "Django views take a request object as an argument, and return a response object, and are called by the framework". Just a matter of degree.
An abstraction layer over a database is not necessarily a framework, it can be just a library. I'm not familiar enough with specific ORMs to comment on those.
A programming language is interesting to look at from this point of view. While sure, you need to use the programming language's features to implement control flow, it typically doesn't actually dictate a high-level control flow itself. There are probably languages where this is not completely true.