This is a bit confusing, do you get 404 errors while downloading or after installation?
404 is a HTML error code, which address is shown in the browser address bar?
I assume that you got this error after installation. Then this is not relevant for you, LibreCAD was installed properly and you can use it. There should be a LibreCAD folder in the programs section of the start menu.
The error, if my assumption is correct, is caused by the Windows installer, which opens the browser after installation to show our donation page. We recently moved to a new server and launched a new website, seems we forgot to migrate the donation page.
Thanks for reporting this, we try to fix it soon.
Armin
investing less than half an hour into Search function can save hours or days of waiting for a solution