Sorry to post to an old thread, but the MU commander tip was an interesting one. After a minute or two of testing, I think I may have found something that might lead to a fix for non KDE systems. I don't use KDE, I prefer Mate, but I take user jostber at his word that drag and drop works in that desktop environment.
For the brain developers, under Mate and probably all gnome based DE's:
#Mu Commander: If you drag and drop from this application into The Brain, a local path string is provided:
#This seems a little unusual but TheBrain recognizes it and it works!!! Woo Hoo!! I have never seen drag and drop work in Linux until now.
#Note: Dragging from TheBrain into Mu Commander does not work.
#Nearly any other Linux program or desktop environment into The Brain: Provides a URL style path:
#Doesn't work. Never has.
To fix dragging at least INTO TheBrain: add a handler in the code for the extra "file://" prefix. Even if you restrict it to only "file://" (ignoring other URI schemes like ftp, webdav, whatever), it would be a huge boost forward.
My system: I'm using Brain 8. I just upgraded thinking drag and drop would be fixed after reading this post, but am again disappointed. I currently use Mate desktop environment (on Mint), but I've used several desktop environments in the last decade; TheBrain has never allowed drag and drop for me. I have always been a paid Brain user, as I know it's handicapped in this respect when in free mode. I've paid for every upgrade since Brain 4, always disappointed each time when drag and drop remains broken...
Hope this might help lead to a fix for Gnome / GTK based desktop environments. It's been a drag. Pun not intended. ;-)