Is it possible to get the .config with which it is built from a running OpenWRT?

Question

Network administration

Actually the question is in the title.
We have some OpenWRT firmware for a certain device. We have an author who, that he will not hand over .config to enemies. Is it possible to get its .config from the finished firmware, by analogy with how you can usually get .config from a Linux kernel? Is he hiding somewhere in the system?
PS The question that, according to the logic of the GNU GPL, the author is obliged to provide .config at the request of the one who received the firmware, let's leave aside, the author of the assembly directly says that he did not care about licenses and, like any Russian, was used to appropriating someone else's.