I've written it for the ATtiny13, ATtiny85, and ATtiny84 series. Other AVRs with an 8-bit timer/counter having output compare could be supported with minor modifications to the code.
It is truly full-duplex, in that a frame can be transmitted concurrently with a frame being received. Received bits are typically sampled within 5 cycles of the center of each bit. With a baud rate of 57.6kbps and F_CPU of 8Mhz, less than 50% of the CPU cycles are used during continuous send and receive.