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...
NEEDS:
1. ImgBurn 2.5.7.0 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