The HB6809 is a mini ITX form factor 6809 based open expansion computer. there are four expansion slots available which are pre-addressed in to 4K sections, providing enough space to build fairly versatile modules. Currently there is a bare bones serial module but more modules are in the works for sound, traditional HID devices like keyboards / mice / controllers, and graphics. You can download the full project files schematics and more on the GitHub or Hackaday.io sites for this project.

The serial expansion card is also available as a shared project as well, though the schematics are simple enough the serial controller could be built on the prototyping area of the main PCB as well.

Libility / warranty language from the licence:

5.1 DISCLAIMER OF WARRANTY -- The Covered Source and any Products are provided 'as is' and any express or implied warranties, including, but not limited to, implied warranties of merchantability, of satisfactory quality, non-infringement of third party rights, and fitness for a particular purpose or use are disclaimed in respect of any Source or Product to the maximum extent permitted by law. The Licensor makes no representation that any Source or Product does not or will not infringe any patent, copyright, trade secret or other proprietary right. The entire risk as to the use, quality, and performance of any Source or Product shall be with You and not the Licensor. This disclaimer of warranty is an essential part of this Licence and a condition for the grant of any rights granted under this Licence.

5.2 EXCLUSION AND LIMITATION OF LIABILITY -- The Licensor shall, to the maximum extent permitted by law, have no liability for direct, indirect, special, incidental, consequential, exemplary, punitive or other damages of any character including, without limitation, procurement of substitute goods or services, loss of use, data or profits, or business interruption, however caused and on any theory of contract, warranty, tort (including negligence), product liability or otherwise, arising in any way in relation to the Covered Source, modified Covered Source and/or the Making or Conveyance of a Product, even if advised of the possibility of such damages, and You shall hold the Licensor(s) free and harmless from any liability, costs, damages, fees and expenses, including claims by third parties, in relation to such use.