ProveSource offer a free forever plan: no time limitation, credit card details or trials required. Using the free plan you can only have one active social proof notification on your website.
ProveSource offers a variety of social proof types generally referred to as "notifications" since we show social proof in a notification style in your website.
In essence, you can only have one type/category show up in your website, e.g.
show only reviews from your Facebook page
show only purchases in your store
show only live visitors in your website