It's the guest OS (Win7) which has to be licensed properly. However, VMware Player has to be licensed too for commercial use! Anyway, instead of reimaging and/or backing up/restoring whole VM's, you may consider to use VMware Workstation, which not only provides the option to create snapshots and revert to them, but also allows to clone (full clone, linked clone) VM's, so that you could run multiple instances from a single base image. Regarding reboots, VMware Workstation contains a command line tool "vmrun" which provides several options, including starting/stopping VMs, and you could run this as a Windows task.
André