It does no checking, but it does record who uses it and at what times. There are tools to read these log files to see if you are exceeding your 'license' usage.
What do you mean by 'valid Creo License'?
FlexNet does the Creo license handling and has no links to Windchill.
If you mean is the license a legal license versus a cracked one. the Creo code has checks for that, not Windchill.