Thanks for Chris Turner and Derrek Landauer for investigating code development for the HCS12 on the Linux Platform.
You need to be able to communicate with the board in Linux and there are at least two programs to do this:  MINICOM and Kermit.  Click the links for tutorials.
Prior to communicating to the Dragon12 board, the mapped location of your serial port is needed. The easiest way to find a Serial device is to type the following into a terminal:
dmesg | grep tty
This command is a collection of other commands working together to list “tty” devices. For information regarding dmesg or grep, click on their respective links. The output should look similar to this:
[    0.004000] console [tty0] enabled
[    1.388067] serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
[    1.388684] 00:09: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
[   13.182823] usb 1-1: pl2303 converter now attached to ttyUSB0
[   16.137926] ttyS0: LSR safety check engaged!
[   16.138410] ttyS0: LSR safety check engaged!
[   19.738332] ttyS0: LSR safety check engaged!
[  252.162725] ttyS0: LSR safety check engaged!
[  252.163311] type=1503 audit(1237312017.197:6): operation="inode_permission" requested_mask="w::" denied_mask="w::" fsuid=0 name="/dev/ttyUSB0" pid=6401 profile="/usr/sbin/cupsd"
Search though the list for remarks that resemble “ttyS*” or “ttyUSB*” (standard Serial and USB-to-Serial devices, respectively), where “* refers to an integer assigned by your machine. For the above example a standard Serial port found is at /dev/ttyS1 and a USB-to-Serial device is located at /dev/ttyUSB0. If no instances of a serial device are displayed, then a device driver is needed which may require specific knowledge of the band and model of the device used, perhaps its chip-set, and a working knowledge of search engines. After a working serial device is found, refer to the Minicom Tutorial to configure and use the Serial port.
Assembling a program in Linux
No currently supported assemblers exist for Linux, but there is the possibility of using WINE to run a Windows version of AsmIDE in Linux.  Click the link for a tutorial.
Advanced Development
You can do further HCS12 development under Linux using the free GNU toolchain (cross-compiler, assembler, etc) for the HC11/HC12. See the links below:
You can also purchase a commercial "Workstation for Linux" program from VMWare. This allows you to set up a "virtual" microsoft system on top of a linux system (you can run microsoft programs without booting out of linux). You can then install Code Warrior in the virtual microsoft system and run as desired. You can have full hardware access including serial ports and the BDM via a parallel port (if you have a BDM parallel port system such as from PE Micro).
Linux and the HCS12