Hi @x-luo, thanks for getting in touch. I am afraid that the Core SDK has now been deprecated and replaced with the Tobii Stream Engine API and Interaction API, so I am afraid we cannot support using the ET5 with the Core SDK however our general licencing model still holds in that so long as your are not storing gaze data or using the data for analysis, and are developing only for interaction purposes, then you do not need to purchase a special licence from Tobii. If you would care to clarify your situation, I would be happy to provide further details or suggestions. Best Wishes.