libcda is in part derived from BCD.  The original licence is below:

  "You may use, modify, redistribute, and generally hack it about in
  any way you like, but if you do you must send me something in
  exchange.  This could be a complimentary copy of a game, an addition
  or improvement to BCD, a bug report, some money (this is
  particularly encouraged if you use BCD in a commercial product), or
  just a copy of your AUTOEXEC.BAT if you don't have anything
  better. If you redistribute BCD or make a game using it, it would be
  nice if you mentioned me somewhere in the credits."

I emailed Brennan about changing the licence to giftware some time
ago, but received no reply.  I'm changing the licence a little anyway,
to reflect the new situation.  Think of it as "relaxed swapware", or
giftware by another name.

  You may use, modify, redistribute, and generally hack it about in
  any way you like, but if you do you should contribute something in
  exchange.  This could be a complimentary copy of a game, an addition
  or improvement to libcda, a bug report, some money, or just a copy of
  your AUTOEXEC.BAT or .bashrc if you don't have anything better.  If
  you redistribute libcda or make a game using it, it would be nice if
  you mentioned the contributors somewhere in the credits.

