Please read the following articles to learn what "Windows Defender SmartScreen" is:
https://www.pcworld.com/article/3197443 ... ws-10.html
https://www.howtogeek.com/75356/how-to- ... windows-8/
Basically, SmartScreen blocks ALL "unknown" programs from starting, because they're unrecognized.
Unofficial Patch 1.5 is actively developed, and Minor Updates are released at least 1 time per month.
You can read the changes log here: https://www.ee2.eu/patch/changes/
This means, that the installer file and other executables in the patch change very often. Due that our community is rather small, the cloud-based protection (SmartScreen) always warns users that the program is "unknown", "not popular".
Besides that, sometimes anti-virus programs are throwing false positives, usually for the same reason (not too many active users).
Recently, Windows Defender Antivirus was detecting the Launcher files as malicious. After my submission, Microsoft has analyzed the file, confirmed that it's safe and removed from their detection definitions. You can read this post on twitter for more information:
However, if you still don't trust in this project, you're not forced to use it. You should google and read reviews about Unofficial Patch 1.5 on other websites / forums to get opinion from other users if it's safe or not.