when opening it windows block it and says its a unknown app?
i also got this when scanning the program
is it a false positive?
The program is unsigned; the installer is a bit old; the client potentially does some insecure things (look at the code yourself to find out, nothing comes to mind immediately). As long as you get the installer from the github release, which usually is the same as the one linked on Etternaonline, it should be fine. The installer is usually what triggers antivirus either on opening or on download.
The installers are made by github automatically and then I personally download and repackage them. I’ve done this for every Windows release since 0.61 or so.
The Windows installer is actually more of a self unzipping archive. You can open the .exe with a software like winrar or 7zip and extract it to wherever you want yourself if you want to avoid running the installer exe.