The FaceRig Pro DLC was designed by people who want to make money by posting content generated by FaceRig online.
The differences between the basic versions and the Pro DLC are:

• You may monetize videos on Youtube/Twitch or similar with FaceRig Classic as long as you earn less than $500 monthly income generated by the channels where this content is posted. This includes advertising-based income and voluntary donations (one-time or recurring, such as Patreon).
• You may monetize videos on Youtube/Twitch with FaceRig Pro DLC, regardless of your monthly income.
• Content created with FaceRig Classic that has been published is governed by the Creative Commons License, while content created with Pro DLC can be made available under any license, as long as it is not sold directly (see below for unrestricted commercial use - with FaceRig Studio).

FaceRig Pro does not bring any new assets, technical features or improvements other than with FaceRig Classic. If you only want to use it for fun with friends and family, there is no reason why you would need the more expensive Pro DLC unless you want to continue to support the development effort of FaceRig.