I just received the BT2S-slave today from Amazon. I will be using this with a Freescale 8bit processor, not an Arduino board. I bought it because it can take a 5V supply. On the bottom of the board though it says 3.3V level by the TXD and RXD pins. Can I not use 5V logic on those?
You should be able to use 5V logic, but it really depends on your system. As long as 3.3 volts is enough to trigger a read on your serial receive side it is no problem, but if you have very large hysteresis it could be a problem.
For example the Arduino is a 5V system, but the Virtuabotix BT2S Slave works perfectly with it because 3 Volts is more than enough to trigger a high reading on the micro-controller.