Now I'm running Directadmin in a Server with Debian 4.0 and all is running without any problem.
http://www.directadmin.com/install.html <- This page shows that directadmin will support Debian 4.0 in the future, but "officially" don't support it but I can update it without any problem and all services are running without problems.
Uhmmmmm I don't know if the installation script of Directadmin run in Debian 4.0 but Directadmin run correctly, but there is a problem now all updates in the stable repositorys of debian have releases for Debian 4.0 if somebody run apt-get update / upgrade or dist-upgrade commands debian will be update to 4.0.
Actually I am running Directadmin in two servers one with debian 4.0 and one with Debian64 (I know that Directadmin don't give support to this distributions) but I don't have any problem, in Debian64 when I install Directadmin I have a little problems with exim installation but I can install exim manually and It is run without problems. The other services run without problems.
Only one question for Directadmin staff. When you will release Directadmin for Debian 4.0 and Debian64? Do you have scheduled the development for this updates?