OK, i have an idea (although your free time, not used for googling is my wasted time used for thinking how to solve your problem).
1. Read info in this link
http://www.chrysocome.net/dd & learn how to use dd command in MS Windows or use your ubuntu live-cd and from there, with dd command put img file on usb-stick -> you need to have an access to your windows disk!)
2. Download DragonFlyBSD .img file form this link
http://mirror-master.dragonflybsd.or....3_REL.img.bz2, untar file & put it with dd command on your bigger usb-stick.
3. Reboot and install DFBSD.