The best replacement for active directory is ldap.

The best alternatives to active directory are rated as following:

★★★★★	ldap
★★★	workgroup
★★★	open directory
★★	novell
★★	openldap
★★	edirectory
★★	domain controller
★	domain
★	samba
★	exchange server
★	radius
★	nds
★	kerberos
★	group policy
★	dns
	adam
	ldap authentication
	exchange
	sharepoint groups
	novell directory services
	nt
	apple open directory
	windows authentication
	domains
	workgroups
	dns first
	identity management

Your alternative for active directory is not listed? Suggest!

Speaking about active directory, one probably shouldn't forget about linux.

Other search terms related to active directory and their ratings are:

★★★★★	linux
★★★★★	ldap
★★★★	bind
★★★	domain
★★★	server
★★★	dns
★★	windows server
★★	kerberos
★★	dhcp
★★	powershell
★★	vpn
★★	linux dns
★★	exchange
★	freenas
★	office 365
★	samba
★	asp.net
★	wins
★	bind dns
★	dns server
★	profile manager
★	router dhcp
★	mac integration
★	windows dns
★	domain controller
	exchange 2003
	exchange 2010
	dhcp server
	samba 4
	roaming profiles
	external dns
	intellimirror
	microsoft dns
	workgroup

You have in mind a companion for active directory and it is not yet here? Propose!

Google Trends

Scale is based on the average worldwide traffic of active directory in all years. Click on graph for more.

active directory

ldap

workgroup