If the traffic between your robot (on the openkapow server) and the web site it is interacting with is encrypted or not depends on if you are using HTTP or HTTPS to interact with those sites. If your robot is using HTTPS in all URLs in Load Page steps etc, then all the traffic between the robot and the site is encrypted.

Basically it is the same way as when you are surfing in a browser. If you are using HTTPS it is safe, if you are using HTTP you are showing all your info to everybody. I am sure that whatever site you are going to use in your robot also supports HTTPS, at least if it is security concious and requires login.