It likely depends on the mfgr. Supermicro calls it SFT-OOB-LIC. HP has standard and advanced iLO. Haven't tried the IPMI interface on Supermicro without a license, but basic power operation might work.
I've used several Supermicro boards across several generations, and never needed the extra license key for remote power on capability. Every server BMC I've ever used from any vendor had that capability standard without requiring the premium option. The features gated behind an extra license are typically things like remote KVM or remote changing of BIOS options.