Yeah that was me that wrote the tutorial. I am the moderator of the Dreamcast side, well now I am a global moderator of the new isozone site but ya.
I worked very hard getting our sdiso section op and got many of my frineds to buy the adapters from Taobao and they have been contributing to the list of games we have. It is amazing what the community can do when we all pull together.
SDL = Sandisk Loader, aka the SD Adapters we have, just another name for them really.
If you are wanting a Dreamcast with no moving drive than I assure you that is what you are looking for. If I had the money myself I would go that rout, but you can still do the same thing without modding your system, just burn the "Dreamshell from SD Loader disc" and it will ONLY spin the disc enough for it ot tell the Dreamcast to boot the Dreamshell Operating System directly from the SD card.
Trust me, this will make the system last for many years to come, and hopefully for many more decades!