I haven't been able to reproduce the virus warning but a google search of "Renpy" and "Virus" gives you dozens of search results showing that it's most often a false positive. However that should not be assumed to be the case every time, I would always recommend a person to err on the side of caution. With that said I use Malwarebytes and I didn't get any warnings about it. I uploaded it to VirusTotal and this is their analysis
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I don't fully understand what some of these codes are but I have not seen any adverse affects on my PC and Malwarebytes and widows defender say the program is safe.
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This seems relevent too.