Yep, its really easy to interface a PS/2 keyboard via an arduino to an apple II.
There is a library for the PC keyboard, calculate the required bit pattern then toggle the strobe.
This is a part of the code I used
if (keyboard.available()) {
// read the next key
char c = keyboard.read();
char_code = int(c);
digitalWrite(_B1,HIGH && (char_code & B00000001));
digitalWrite(_B2,HIGH && (char_code & B00000010));
digitalWrite(_B3,HIGH && (char_code & B00000100));
digitalWrite(_B4,HIGH && (char_code & B00001000));
digitalWrite(_B5,HIGH && (char_code & B00010000));
digitalWrite(_B6,HIGH && (char_code & B00100000));
digitalWrite(_B7,HIGH && (char_code & B01000000));
digitalWrite(Strobe,HIGH);
digitalWrite(Strobe,LOW);