You can access the newlib source in a few ways:

Anonymous CVS read-only access to the newest source
  cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src login
  {enter "anoncvs" as the password}
  cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src co newlib
Read-only web-based CVS access to the newest source

You can use the cvsweb interface.

Source snapshots

Source snapshots are available as gzipped tar files via anonymous FTP from the newlib ftp directory. New snapshots are packaged and released from time to time. Documentation snapshots are also provided.