BikeCAD and BikeCAD Pro are written in Java. The Java code is compiled and bundled in a JAR file (JAR stands for Java Archive). This JAR file can run on any computer where the Java Runtime Environment has been installed. It doesn't matter what operating system is being used. The same JAR file runs on all systems.
The only reason there are different versions of BikeCAD Pro for different operating systems is because the Mac and Windows versions include the option to place an icon on the dock of a Mac or on the desktop of a PC. To facilitate this, the Windows option comes bundled in an executable setup file. The setup file creates a folder in the Windows operating system for BikeCAD Pro (the default location for it is: C:\Users\yourUserName\AppData\Roaming\BikeCAD Pro 11.5\). It also gives you the option to create a desktop icon and/or an icon in your Start menu. The Mac version is distributed as a code signed Mac app and comes in a zipped folder that includes an icon that can be dragged onto your dock. The Mac version has the Java Runtime Environment built into it. Therefore, you do not need to have Java installed on your system to run the program. A second Mac version is available for older Macs that may be incapable of using the latest Java Runtime Environment. This version only requires Java 1.5 or higher.
The Linux version of BikeCAD Pro is downloaded in a zipped file. This file should be unzipped to create a folder called BikeCAD Pro. Inside this folder will be the bikeCADPro.jar JAR file. BikeCAD Pro is launched by clicking on the BikeCAD JAR file. It is also possible to set up an icon in Linux as described here.
BikeCAD Pro will by default be rendered with the default Look and Feel of the operating system it is being run on. If desired, you can change the Look and Feel according to the instructions at: bikecad.ca/look_and_feel.