My bad, it works! How can I create an alias?
Thanks for the donation of 1NMC

. Hope to send them back soon :p
You must register an alias prefixed with "id/" in namecoin.
Here is mine to give you an idea :
namecoind name_show id/khal
{
"name" : "id/khal",
"value" : "{ \"email\" : \"khal@dot-bit.org\", \"bitcoin\" : \"1KHAL8bUjnkMRMg9yd2dNrYnJgZGH8Nj6T\", \"namecoin\" : \"N1KHAL5C1CRzy58NdJwp1tbLze3XrkFxx9\" }"
}
Fake example of registration :
namecoind name_new id/bitinvestor
[
"045637420d7820779426b3a9da847253070e9b51ffc6dc8bfd46fd7cf9bdf529",
"94086936402036f000"
]
namecoind name_firstupdate id/bitinvestor 94086936402036f000 045637420d7820779426b3a9da847253070e9b51ffc6dc8bfd46fd7cf9bdf529 "{ \"email\" : \"khal@dot-bit.org\", \"bitcoin\" : \"1KHAL8bUjnkMRMg9yd2dNrYnJgZGH8Nj6T\", \"namecoin\" : \"N1KHAL5C1CRzy58NdJwp1tbLze3XrkFxx9\" }"
To be sure you put a valid json "value", copy/paste the value here :
http://dot-bit.org/tools/domainCheck.phpps : don't use more than 520 characters to avoid a bug that will be solved soon.