The patch for DNSSEC-Tools support was included in Version 3.2.4 of ncftp.
Last tested: ncftp 3.2.4 and dnssec-tools 1.6, in July of 2010.
Enabling DNSSEC-Tools support
Verifying DNSSEC validation
Assuming a default configuration where validation is ignored for all hosts except dnssec-tools.org:
$ ncftpls ftp://nosig-A.test.dnssec-tools.org nosig-A.test.dnssec-tools.org: untrusted DNS response. ncftpls: cannot open nosig-A.test.dnssec-tools.org: unknown host.