PS2 keyboard library and web page for Teensy3

I read that teensy3 is supported since 2.4 version of the library. But on the webpage, it says the PS2 requires 5V, so I assume that its outputs will also be 5V ? Is it OK to just put some protection resistor between the minidin socket and the teensy3 ?

BTW, the simpletest.pde example was not upgraded to include Teensy3 in the list, but that's purely editorial of course...

Maybe this isn't the right place to post the question ?

The Teensy3 I/O is not 5V tolerant. While a resistor may work the best way to accomplish this is to use a logic level shifter, e.g. this 8-Channel version offered by Adafruit. IIRC they also make a 4-Channel version.

Also there is a thread on this board introducing an Arduino to Teensy3 adapter board that does that (and a number of other things ;-)
I don't think it's in production yet, so this may be interesting for future projecrs requirring 5V signal conversion.

PS2 keyboards normally use open collector signals. A resistor pulls the line high. The circuitry only shorts the pin to ground. It's very similar to I2C signals.

Even if the resistors are connected to 5V, the current they can deliver is well below the 10 mA maximum injected current spec. So you probably do not need a special buffer chip.