Since the upstream repository disappeared, I seem to have one of the
only copies left in the universe.

This is what SVN info says:

Path: .
Working Copy Root Path: /home/anarcat/src/alternc-slavedns
URL: https://alternc.org/svn/alternc-slavedns/trunk
Relative URL: ^/alternc-slavedns/trunk
Repository Root: https://alternc.org/svn
Repository UUID: f84471de-540d-0410-a634-8ee2f8b0224d
Revision: 4875
Node Kind: directory
Schedule: normal
Last Changed Author: anarcat
Last Changed Rev: 4874
Last Changed Date: 2014-05-07 11:01:45 -0400 (Wed, 07 May 2014)

Obviously, history is not available because alternc.org/svn has
disappeared and SVN keeps only the last version on checkout.