CSS does have bots and DoD classic has Shrikebots and Sturmbots, but there haven't been any mods for DoD Source. Additionally the Sturmbot developer died in an accident (presumed dead anyway), and all of the code was in his head and not backed up anywhere, so Sturmbots won't appear in DoD:S anytime soon. I have no idea if the Shrikebot guys are working on DoD:S...check their site for an update.
DoD:S DOES include bot code, but the bots have no AI associated with them. Go into console and set SV_CHEATS 1 and type BOT, a new bot player on the current team you are on will appear at spawn..
A max of 6 or 7 bots will appear, but they will move randomly and not shoot.
Hope this helps your question, Skylit.