In the time that has passed since I first lamented the DS' limited ability to execute independent applications Nintendo DS development has become increasingly mainstream, and along with that a slew of affordable and easy-to-use NDS flash cards have become available that allows independently developed applications to be executed on the DS. There's even a retail flash card now - the "Games 'n' Music" cartridge. I'm not linking to it... it lacks the file system drivers that make it a useful device. But it's the first flash cartridge (that I know of) that's widely available in retail channels such as your local neighborhood BestBuy.
I picked one up, just to see what it was like. It lacks DLDI support, which means it can't interact with the filesystem. If it can't interact with the filesystem, that means no save games, no loading libraries, no loading maps, no user profiles. Blech.
But it's in retail, which makes it interesting. And it boots DS Linux, which is at least mildly intriguing. At it's cheap... only $35 for the flash card, 128 microSD card and a microSD USB reader. I might waste an equal amount on a craptastic NDS title... so I don't feel too entirely guilty about buying a flash cart that's missing a DLDI.
I think I understand why Datel didn't offer DLDI support. By disabling DLDI people can't execute pirated ROM's from commercial cartridges - instead people are stuck with pure homebrew that doesn't require local storage. This could possibly limit ROM execution of course... but this also wrecks a lot of homebrew.
Thus far I've booted Linux, tried a video and failed to play one homebrew title. Maybe this will eventually gain usefulness once the cart's filesystem is cracked, but until then it may just stay in the bag.