The FreePBX Distro is maintained and put out by the FreePBX.org project. Lots of other companies will bundle FreePBX GUI on their own LAMP (Linux, Asterisk, MySQL, PHP and Asterisk) stack, but that does not mean those systems are the Official FreePBX Distro.
If you are using the Official FreePBX Distro, you will be able to see its version number.
If you are using the Official FreePBX Distro, you will see its version number after you execute the appropriate command below.
On newer systems, execute the following command from the CLI:
On older systems, execute the following command from the CLI:
Open the System Admin module in the GUI, and look for the PBX Firmware version number in the module's home page:
If you do not see the PBX Firmware version number, you are not using the official FreePBX Distro.