I am researching using RFID for a project. I've read a lot about active RFID tags, such as this one. The sites that explain active RFID generally don't say much about the readers. Is a reader for an active RFID tag any different from a Passive RFID reader? Also, do the readers need to be set for the correct frequency? As in, do I need a 433 MHz reader to read a 433 MHz tag?
Yes, they need special readers. Yes, for a 433MHz device, you will need a 433MHz reader.
There is no ISO standard for active tags, AFAIK. Each vendor will have its own protocol, MAC and application layers, so you are basically locked to that vendor (or small group of vendors as in the case of LoRA).