Manually download & extract the "Linux i386 - 32bit" server from here (they don't provide a wget-friendly link).

Edit "ventrilo_srv.ini", key settings are:

Name=Zomtalki 9000          # Server name
Phonetic=Zomtalki 9000      # Server name (for TTS)
Auth=1                      # Require a user password?
AdminPassword=XXXXXX        # Password for admin
Password=YYYYYY             # Password for general access
...
VoiceCodec=3                # Set the codec to Speex to allow Mac clients to join (default codec (GSM) doesn't work for Mac)
VoiceFormat=6               # This is basically the bitrate (see below)
...

To launch:

./ventrilo_srv

Here's the full list of choices for codec/format (from here):

Codec Format Description:
0 0 GSM 6.10 (8 KHz, 16 bit) 1625 bytes/sec
0 1 GSM 6.10 (11 KHz, 16 bit) 2210 bytes/sec
0 2 GSM 6.10 (22 KHz, 16 bit) 4420 bytes/sec
0 3 GSM 6.10 (44 KHz, 16 bit) 8905 bytes/sec
1 0 DSP Group TrueSpeech (8 KHz, 16 bit) 1056 bytes/sec
2 0 Lernout & Hauspie (8 KHz, 16 bit) 600 bytes/sec
3 0 Speex (8 KHz, 16 bit, 0 Qlty) 424 bytes/sec
3 1 Speex (8 KHz, 16 bit, 1 Qlty) 620 bytes/sec
3 2 Speex (8 KHz, 16 bit, 2 Qlty) 865 bytes/sec
3 3 Speex (8 KHz, 16 bit, 3 Qlty) 1110 bytes/sec
3 4 Speex (8 KHz, 16 bit, 4 Qlty) 1110 bytes/sec
3 5 Speex (8 KHz, 16 bit, 5 Qlty) 1502 bytes/sec
3 6 Speex (8 KHz, 16 bit, 6 Qlty) 1502 bytes/sec
3 7 Speex (8 KHz, 16 bit, 7 Qlty) 1922 bytes/sec
3 8 Speex (8 KHz, 16 bit, 8 Qlty) 1922 bytes/sec
3 9 Speex (8 KHz, 16 bit, 9 Qlty) 2384 bytes/sec
3 10 Speex (8 KHz, 16 bit, 10 Qlty) 3168 bytes/sec
3 11 Speex (16 KHz, 16 bit, 0 Qlty) 620 bytes/sec
3 12 Speex (16 KHz, 16 bit, 1 Qlty) 865 bytes/sec
3 13 Speex (16 KHz, 16 bit, 2 Qlty) 1110 bytes/sec
3 14 Speex (16 KHz, 16 bit, 3 Qlty) 1355 bytes/sec
3 15 Speex (16 KHz, 16 bit, 4 Qlty) 1698 bytes/sec
3 16 Speex (16 KHz, 16 bit, 5 Qlty) 2188 bytes/sec
3 17 Speex (16 KHz, 16 bit, 6 Qlty) 2678 bytes/sec
3 18 Speex (16 KHz, 16 bit, 7 Qlty) 3070 bytes/sec
3 19 Speex (16 KHz, 16 bit, 8 Qlty) 3560 bytes/sec
3 20 Speex (16 KHz, 16 bit, 9 Qlty) 4344 bytes/sec
3 21 Speex (16 KHz, 16 bit, 10 Qlty) 5324 bytes/sec
3 22 Speex (32 KHz, 16 bit, 0 Qlty) 669 bytes/sec
3 23 Speex (32 KHz, 16 bit, 1 Qlty) 1061 bytes/sec
3 24 Speex (32 KHz, 16 bit, 2 Qlty) 1306 bytes/sec
3 25 Speex (32 KHz, 16 bit, 3 Qlty) 1551 bytes/sec
3 26 Speex (32 KHz, 16 bit, 4 Qlty) 1943 bytes/sec
3 27 Speex (32 KHz, 16 bit, 5 Qlty) 2433 bytes/sec
3 28 Speex (32 KHz, 16 bit, 6 Qlty) 2874 bytes/sec
3 29 Speex (32 KHz, 16 bit, 7 Qlty) 3266 bytes/sec
3 30 Speex (32 KHz, 16 bit, 8 Qlty) 3756 bytes/sec
3 31 Speex (32 KHz, 16 bit, 9 Qlty) 4540 bytes/sec
3 32 Speex (32 KHz, 16 bit, 10 Qlty) 5520 bytes/sec