I haven’t tried these so I cannot comment on their quality. But this has a list. Of particular note is RetroArch, OpenEMU, and Gens as three FOSS options.
Edit: Also, alternativeto.net is usually a decent source for finding alternatives for specific software. Here’s the list for Kega Fusion alternatives. This has some more options than the other link I provided.
I haven’t read the article, probably won’t, doesn’t really interest me. But I thought the title pretty clearly implies you don’t play as the shooter. I’m surprised others didn’t interpret the same way.