The link83 bios is a version of the dreamcast bios modified by a person with the handle "link83." It combines a region free dreamcast bios with the unique opening animation and sound from the katana development kit.
This is what the dev kit opening animation looks like:
Any way you do it, it costs a little bit of money to get this done. You can buy a blank chip, solder it to the DC motherboard and flash the bios to it via dreamshell, you could buy a preflashed chip from some users on other popular forums, or you can just send your dreamcast off to get modded by someone else. This last one is probably the most expensive option, but since I don't own a soldering iron at the moment and I don't trust myself to do micro soldering on the level the mod requires, that's what I ultimately did.
I recently got my modified DC back, tested it, and here's what I think.
-play DC gdroms from any region without having to use any bootdisc
-have a different opening graphic whenever your dreamcast boots up
-when you are in the music cd player, you can now see the custom artwork that shows up from foreign gdroms if there is any, and also play CDDA tracks on foreign GDroms (an unmodified DC would treat a foreign GDrom as a CD, and not read from the high density game data layer, thus CDDA music in the high density area, from games like gigawing or voot, would not show up if they failed the region check)
-to be a little picky, on my machine, the new opening graphic starts playing the sound half a second before anything shows up on the screen (while the screen is still black). The new graphic is animated slightly choppier than the stock DC boot graphic. I saw both of these aspects on youtube before I decided to get the mod done, but figured it was related to youtube choppiness. It makes me wonder if the sound and picture are out of sync. But to be fair, it's still pretty neat to just see the new graphic play, and you can still skip it with the start button.
-your dreamcast is no longer "factory perfect" in case that matters to you
Ultimately, should you get this done? I think it makes a lot of sense if you have a sizeable import collection. Although it's very simple to boot foreign games via any of the bootdiscs, I find I play my imports more now just because of the ease of merely putting it in like a normal game and not having to spend 2 minutes with the boot disc each time. I also don't encounter any dour looks from my gf since I don't have to boot up gameshark and have the giant breasted soldier woman pop up on the screen
I give this bios a 9