DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
HashOver - HashOver is a PHP comment system intended as a replacement for services like Disqus.
Juvia - A commenting server similar to Disqus and IntenseDebate
talkatv - talkatv is an open source comment service much like ...
LiveFyre - livefyre-subscriptions - A isomorphic JavaScript library for managing Subscriptions in Livefyre's Personalized News Stream service.
Commentics - Commentics is an advanced PHP comment script with many features.