There are some addons that are the result of collaboration, like the Star Wars addon. Others are work of individuals.
As a rule of thumb, whoever wants to make those addons available in workshop should make efforts with all possible means it has in contacting the original authors and ask for permission. Being material available in this forum, a request for permission via PM seems the viable option.
If no one is responding after a while, and I'd chek also in their profile if the user has not logged in for quite some time, then the conversion of the addon for its fruition in workshop, provided it's working as intended, could be fair use from my point of view.
The user in question has specified with a rather standard disclaimer in those workshop addons that he will pull off those addons if the original creator makes that request. Here I'm hoping that the user tried indeed to contact the creator via PM before publishing that material, rather than use right away the lazy option of that standard disclaimer. The reason is that those creators could not have a steam account, thus a steam version of SpaceEngine, and simply be unaware of the contents of the workshop nor being able to request their material pulled off.
If that's the case, and someone wants to contact that user for such a request, feel free to contact me in PM and I'll report that request to the user via Steam.
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