I'm sorry to see that BikeCAD for Older Macs seems to be having issues on your system. You were right to choose that version as the Code Signed version for newer Macs will not run on Mac OS X 10.6.8. I will continue to investigate solutions to getting the version for older Macs working for you. However, a more immediate solution would be to download and run the Linux version of BikeCAD.

The Linux version should actually be called the universal version. As it can really run on any OS that is capable of running Java. It just hasn't had any extra packaging done to it which the other versions have had to make for easy installation on specific operating systems.

Running the Linux version on your machine should still be easy. It can be as simple as double clicking on the JAR file. It just won't have an icon associated with it that you can drag to your dock the way the Mac version would.