You give your server.exe away for free, and make all of your revenue in value-add hosting, and maybe professional services stuff to specific customers. You still have to maintain server.exe -- fix bugs, add features, etc. -- which requires engineering resources, time, money.
Someone else comes along, downloads your server.exe, and offers hosting and professional services themselves, as a competitor. To a customer there is no difference between you.com and competitor.com, they're hosting the same thing on different domains. And the competitor gets their revenue the same way you do, but they don't have to spend anything on server.exe, because you're doing all that work already.
Again, this math doesn't work out, at least not for you. The competitor will always come out ahead.
If the claim is that you have some unique ability to produce revenue that isn't available to third parties that download and use your server.exe, then whatever that is, it's not part of the server.exe, just by definition! You've got the server.exe you offer freely, and a different my-server.exe that only you can operate and which has value that only you can extract. So we're back to square one.