It is not dangerous, it only means you have three versions built on your

system, but the only one that can work is the one active, lying in

${prefix} (the other (in fact, all installed versions, the active

version only makes links to this place) are kept in

${prefix}/var/db/dports/software/) that way you can roll back to an

older version if the new one does not work well. However, it takes space

on your hard drive.

To uninstall one version, just use "uninstall", for example 

sudo port uninstall apache2 @2.2.0_0

To do a rollback, you have to deactivate the active version then

activate the older one, for example:

sudo port deactivate apache2 @2.2.3_0

sudo port activate apache2 @2.2.2_1

(I do not know about your ruby problems...)