I think not really. Freemarker already has a (generated) bnd.bnd file.
They have an ant-task (ant clean jar ide-dependencies) which prepares the project for importing it into an IDE like Eclipse and it uses bnd to create the bnd.bnd file. (they are discussing moving to maven or gradle… but at the moment still ant).
I import this project into a fresh Bnd workspace locally
which compiles and produces a nice generated/org.freemarker.freemarker.jar
Via -buildrepo: MavenLocal I push it to a local Maven repo from which I consume it in another Eclipse instance via my repo (see my other topic). (Note: The other Eclipse instance is running our application which uses Freemarker. This setup makes it easy to test app-specific things while still being able to contribute to Freemarker e.g. for improvements we need for our app).
This workflow works fine for me.
BUT: I now realise a flaw in my initial question 
I was asking to put the cnf inside the the freemarker project. This is nonsense I realize now - since the bnd workspace lives “around” it, containing the cnf folder and the freemarker bundle / folder.
So I guess I asked the wrong question.
Maybe my question should have been:
How could somebody else replicate my workspace setup (consisting of cnf + org.freemarker.freemarker) from my screenshot above?
Is it manual (as I do it) and I can only send somebody a written recipe?
Or is there a way to put “something” in git, somebody checks it out, executes a command and has the same workspace as I have?
I don’t know if this somehow relates to your answer @pkriens