The Smartscreen filter of MS Internetexplorer/Edge reports OpenAndroMaps website as “unsafe”.
If you have doubts about the integrity of OpenAndroMaps please perform a check on a meta-virusengine like Virustotal or a similar service. These services checks a website against the databases of numerous virustools of high reputation like Bitdefender, Kaspersky, Avast, etc..
In case of OpenAndroMaps the result ist : Clean Site
If you have already installed a solid virustool on your machine or mobile device there is no need for MS Smartfilter cause most of these tools are scanning the traffic of many webbrowsers (not only MSIE/Edge) and check downloaded fieles too.
There is a document on the MS support site that teaches how to report a false positive to Microsoft or how to disable the Smartscreen filter (in case that you already installed a virustool):