Net::LDAP not being maintained is not an issue. In fact, it points to the fact that LDAP as a technology is currently relatively static because it does it's job, works quite well, and is extensible without having to muck with the internals of LDAP.
Just because something isn't obviously maintained isn't enough to signify a dead/rotting library. You need to look into its maturity level, and whether it is being used a lot. LDAP is a wonderfully useful tool, that is used a lot, but it's quiet enough that many smaller shops may not have been introduced to it yet. The fact that Active Directory is built on top of LDAP is something Microsoft would rather not advertise. But that fact alone is enough to tell you that it won't be going away any time soon.