Former Sift intern here.

Sift Science also has both Javascript and server side APIs. See https://siftscience.com/docs/rest-api for info on the REST API. This allows companies to send all relevant transaction and behavioral data to Sift even for users who don't execute Javascript.

Not sure how you would figure that...my take on Sift is that they utilize pattern recognition to determine risk level of a transaction for the seller. Basically, the goal is thwart fraudulent transactions before they get to delivery status.

EDIT: I just checked out what you mean, since Sift utilizes Javascript code for their api call to determine risk, I agree with you...it would render their pattern check ineffective for the Javascript api integration...they need to run server side code, which Sift offers in their REST API.