This page is truly ancient and obsolete. You shouldn't use anything here. Current versions of PCB are hosted at geda-project.org.
"Pcb is a handy tool for the X Window System to design printed circuit boards." It is licensed under the GPL. I use it successfully for my small part of the SNS project on a Red Hat Linux system.
Unmodified pcb links:
My modifications for local use:
Note (14-Jan-2002) that all my library extensions given in the above patches appear to have made it into Harry Eaton's development tree, and will show up in his forthcoming 2.0 version.
Larry Doolittle, LBNL