If I copy GPL-licensed code into my BSD-licensed library, none of my code has to be relicensed.
Yes it does, that's a pretty central feature of the GPL. See section 2.b. of the GPL (v2):
b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.
Yes it does, that's a pretty central feature of the GPL. See section 2.b. of the GPL (v2):
b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.