Just want to note, that ImDisk, mentioned here in the thread, while technically GPL too, can be stripped of non-GPL code easily, according to its author.
Interesting. I was not aware of ImDisk. Reading about it, it appears to be a RAMDisk only tool. Did I misunderstand?
"ImDisk is a virtual disk driver for Windows NT/2000/XP/Vista/7/8/8.1/10 and Windows Server 2003/2003 R2/2008/2008 R2/2012/2012 R2, 32 and 64 bit editions. It can create virtual hard disk, floppy or CD/DVD drives using image files or system memory."
That still misses the point, that it provides a protocol dubbed "devio", that enables userspace programs to create these disks virtually, and handle access via own implementations of write/read primitives.