That means the article directory is allows you to post an article but the link will be nofollow. Nofollow links prevents the article directory from passing valuable link juice to your site for higher ranking. But it adds more credibility to your site's overall link profile.
So, I advice that you still post an article there. It will be good for your site's link popularity.
One of the most recent examples of Google Bomb is "Santorum" which is the last name of a former US senator and presidential candidate. Unfortunately for him, his name is now infamously known as a by product of sodomy. Try searching Santorum on Google and you'll find out.
Hi John and all,
There is no required limit as to how many directories one should submit to in a given day. So submit as many as you can. But avoid submitting to auto-approved directories since many of these have low PageRank. Low PageRanks sites (those with zeros or n/a) can bring down your site's search rankings.
Plus, most of these auto-approved directories are hosted from the same server, thus, if your site has many backlinks in them, this can be detected by search engines as spamming and your site's ranking will go down eventually.
To avoid such disaster, submit only to high quality directories. Although the approval may take time (weeks or even months), the benefit would be high quality backlinks and better SERP positioning.