paskali: Hi, I'm the developer of Fluff and I apologize that I have not seen your crash report and responded until now. I've been mostly away from Tiny Core figuratively speaking, for about two years. Fluff was developed for use primarily with FLWM window manager. I had another developer work with me for a short time that I believe looked into issues with JWM, but he is not involved any more. If you want to stay with JWM, I'm sure you have found something else that will work for you. Back when I used Puppy Linux on JWM, I used the default Rox Filer, and it worked well, after I got used to it.
Fluff has been tested on Gnome 2 and and with Enlightenment it worked OK on those (after some tweaks for E17). I may get back into Tiny Core at some point, but I imagine I won't be actively supporting JWM with my FLTK apps. Hope you find good alternatives!