I just checked the src and apparently if you do have libdns, it will use it, but it's certainly not required.
config.log:
configure
checking for gethostbyname in -ldns
configure
gcc -pipe -o conftest -g -O2 -Wall conftest.c -ldns -lnsl >&5
/usr/lib/gcc-lib/i686-pc-linux-gnu/3.2.3/../../../../i686-pc-linux-gnu/bin/ld: cannot find -ldns
collect2: ld returned 1 exit status
configure
$? = 1
configure: failed program was:
| /* confdefs.h. */
Compiles just fine without it.