Announcement of the name change [1]
Links to various documents with information about the upgrade/conversion process:
dahdi-linux (kernel modules) UPGRADE.txt [2]
dahdi-tools (command-line tools) UPGRADE.txt [3]
Asterisk 1.4.22 notes about converting from Zaptel to DAHDI [4]
Asterisk 1.6.0 notes about converting from Zaptel to DAHDI [5]
Links:
[1] http://blogs.digium.com/2008/05/19/zaptel-project-being-renamed-to-dahdi/
[2] http://svn.digium.com/view/dahdi/linux/tags/2.0.0-rc3/UPGRADE.txt?view=co
[3] http://svn.digium.com/view/dahdi/tools/tags/2.0.0-rc2/UPGRADE.txt?view=co
[4] http://svn.digium.com/view/asterisk/tags/1.4.22-rc3/Zaptel-to-DAHDI.txt?view=co
[5] http://svn.digium.com/view/asterisk/tags/1.6.0-rc4/Zaptel-to-DAHDI.txt?view=co