Version 5 license files work only with the Version 5.x series of products. You may easily run Version 4.2 or earlier versions of Acucorp products alongside Version 5.x products. To do this, simply install the products and license files in a separate directory for each version.
For example, if you place the Version 4.2 compiler and license file in the "C:\Acucobol42\AcuGT" directory, and place the Version 5.0 compiler and license file in the "C:\Acucorp\Acucobol500\AcuGT" directory, either version of the compiler will execute properly.