The MSDOS/MSWin32 command-line mobigen binary (v6.2 build 43) is still available directly from the
Mobipocket Developer Center.
The direct link to the official file is:
http://www.mobipocket.com/soft/prcgen/mobigen.zip
The official (but alpha) Linux version is also available directly from Mobipocket, but isn't linked to anymore from the developer page:
http://www.mobipocket.com/soft/prcge...n_linux.tar.gz
This is the version with the symbols stripped.