I just played it online with my NTSC/U Dreamcast. I will provide a link (below) to Dreamcast-Live which will allow you to download what you need to connect - if you do not have what Jako listed (above my reply). These are legit downloads, so what you may need is the following...
1. ImgBurn 18.104.22.168 for Dreamcast (follow the directions being there are a couple of files you'll need to copy to a designated subfolder).
2. Sylverant Planet Ring Patcher v2.0 - OR - Sylverant PSO Patcher v2.0 (use this one).
3. A blank CD-ROM.
Link to Dreamcast-Live Downloads:http://www.dreamcastlive.net/downloads.html