A passive sensor does not need any additional energy source?
There are no strict, formal definitions of "passive sensor" and "active sensor". These terms can have different meanings based on the context in which they are used. Both of the quoted paragraphs are basically correct but they have different contexts.

Regarding the "additional energy source", this would typically be a battery or similar power supply. The word "additional" here means a source in addition to any energy provided by the sensor itself. In many cases the sensor itself provides no energy so the "additional" energy source is "in addition to the sensor" not "in addition to a another energy source".