Yes you can use the DI-614+ to share a dialup connection with wireless clients.
Go into the admin settings for the router and disable DHCP, so your router will effectively become a simple switch. Plug in your sharing computer and setup ICS. Then as long as your sharing computer is on (and thus assigning IP addresses via the router to all wireless clients) you can add clients (wired or wireless) to the network, which in turn can share the dialup connection.
With DHCP disabled the DI-614+ is nothing but a 4 port AP.