The hardware/software requirements for a developer license of Server 15 are the same as for a commercial license. Only difference is the license key and the limit on number of connections.
I have it running on Windows 7 Pro.
I suppose there's a difference between "can" it and "should" it. More precise to say it's not supported. But I'm a mac guy, so what do I know about Windows? As little as I can get away with ;-)
If you try it and it runs then great, but it won't be supported and you're unlikely to get any help with any problems you have.
Years ago a customer bought the Small Business version of Windows Server, which was not supported, ignoring our recommended specification. However, going through the server and removing all the services that would clash with those required by FileMaker Server ended up with a perfectly good FM Server that gave long reliable service.
If you're using it for development only and can get it to run, then fine but Philip is right; the recommended specs require:
Windows Server 2012 R2 Standard Edition with Update
Windows Server 2008 R2 SP1 Standard Edition
Windows Server 2008 R2 SP1 Enterprise Edition
However, I strongly recommend that you do not try this for non-development purposes.
I don't know about Windows 7 but I have it running fine on Windows 10 pro for development.