For some reason all links for blue card gateway are dead. This file is not mine and I know that none cares about gateway anymore, but still some people may want it so here it is
How to use it:
1) format your microsd to fat32
2) extract the zip file
3) copy all content from zip file to the micro ds
4) create a folder with the name "Games"
5) paste all .nds (all your ds games) files you want in Games.
6) Your Gateway is ready for use, just run it and it works
WARNING: As far as I know gateway is not supported anymore, so if you have any kind of problem you are on your own.