I had been living under apparent false impression that "realfft.c" on which the FFT implementation in DMLIB was basically copied from was released in public domain at some point, but it could very well be that it never was. Correct license is (or seems to be) GNU GPL. Thus I removing the code from DMLIB, and profusely apologize to the author, Philip Van Baren. It was never my intention to distribute code based on his original work under a more liberal license than originally intended.

--- a/Makefile.gen	Fri Mar 11 16:27:33 2022 +0200
+++ b/Makefile.gen	Fri Mar 11 16:32:50 2022 +0200
@@ -302,7 +302,7 @@
 DMLIB_OBJS += \
 	dmfile.o dmlib.o dmcurves.o dmstring.o \
 	dmgrowbuf.o dmargs.o dmvecmat.o dmperlin.o \
-	dmimage.o dmengine.o dmfft.o dmzlib.o \
+	dmimage.o dmengine.o dmzlib.o \
 	dmlicense.o