Site looks legit. They sell a Pro version of this app. Hopefully, you can play this file with the free version.
Plus, they have other free and pay apps for OS X and for different web browsers on OS X.
I don't see anything about the site that looks malicious.
I am really surprised that VLC couldn't play the file.
at least some eltima software used to add kernel extensions to the system, which is unusual for a video player/converter...
if it's just an application, requiring no 'install' and it doesn't ask for a password... you should be ok, but otherwise be clear on how to remove it fully beforehand.