Hi @takashimatsuzawa and thanks for your query.
Regarding analytical use, so long as your application has the intention for use as an interaction application with no analysis or long term storage made of the gaze data itself, then you should be fine to continue as normal. If you would care to expand on the project intentions, that would be most helpful.
With respect to the data that is exposed with the Stream Engine on Windows vs Linux, there is no difference so you should be able to port your application (assuming you are using the c++ bindings) between the operating systems without much difficulty. That being said, porting a UWP application even in a virtual environment on Linux is not something officially supported or recommended.
Finally, yes we can confirm that a proper calibration is necessary to extract gaze data locations, as individual calibrations are highly variable so no “generic” calibration is supported.
Please let us know any further information we can provide for you. Best wishes.