I never used a "Positive" SSL domain addon...but I know what an SSL is!
-----The information below is just to inform those that doesn't know what SSL is: -----
SSL stands for Secure Sockets Layer this is a web protocol developed to provide domains or websites a secure date transmittion. It is encrypted in a special string so that the data won't get cracked too easily. However "Positive" SSL has a slight difference in comparison to "normal SSL". Positive SSL is developed by Comodo Security company, it provides a higher security data encryption to make your domain even secure, its just an additional addon to your domain that makes it more secure. I don't think it is neccesary to enable it unless you are trying to use commercial grade credit card transactions... :smile: