I'm looking for a IRCd software which can effectively prevent channel takeovers. I had something in mind like channel ops have to log-in by password to gain op status and are not allowed to op other chatters, similar to moderators on boards like this. is there IRCd available that allows this?

Try installing the standard services, ChanServ, NickServ & MemoServ.

You can get a version here (http://anope.org/index.php).

I've never seen an actual IRCd that will prevent this. Xyrael is correct, standard services should solve your problems.