faceoffIM will always be free, however it is something I do in my spare time, and your donation will go toward coffee (or beer!) for me to sit up 'til ridiculous early hours of the morning, writing and improving the software for everyone that uses it.
So if faceoffIM has let you get away with chatting to your friends while at work/school and you feel like showing your appreciation, why not donate? Using my PayPal donation button on the right, you can donate whatever amount you feel like, even if you only want to give $1 (hey, if 4 people do that that'll buy me a coffee or a beer!)