Using the mozillaAbPersonAlpha schema:
I was able to open the schema in LDAP Studio and export it to an LDIF. The problem I encountered was that the exported LDIF had a typo which caused the import to fail. The typo was in this section:
dn: ou=macthingRules, cn=moz, ou=schema
"macthingRules" should be spelled as "matchingRules", otherwise the import into Apache DS fails.
Once I repaired this manually, the import worked without any errors.