The <ldap-server> tag (see http://static.springframework.org/spring-security/site/reference/html/ldap.html#d4e1399) allows starting an embedded Apache DS instance.
It currently uses Apache DS version 1.0.2. The latest Apache DS version is 1.5.4.
The 1.5 branch of Apache DS has numerous improvements over 1.0, and is more stable and faster than 1.0. Unlike 1.0 it's also actively maintained.
It has additional features that are important for unit and integration testing (which <ldap-server> tag is intended for) like support for dynamic schema and dynamic configuration.
For those reasons Spring Security should be updated to use the newer Apache DS branch.