I'm so happy because my info. was usefull. you asked
me 3 questions and I try  to answer  them respectively.

1. as I mentioned in my prevous mail, openLDAP is an
open source, so you shouldnt pay. another benefit is,
it is a lightweight directory, it needs almost 20MB
disk and over 3MB memory space. In addition, it
installs easily. Furthermore, you can add and modify
its schemas easitly.also, backup and recovery is fast
and easy(slapcat).the most important point is, it
works on every platforms(windows, linux,...) and it
can work on home edition version  of windows. general
speaking it is light, fast, free and secure. However,
it doesnt support RDN(Relative Distingush Name)and in
comparision with AD, ACL configuration is not so easy
in openLDAP.

2. I dont understand it exactly, could you plz, give
me more details about it. you can conn. to AC with
JNDI or via its browser? and can you list your users
by using JNDI? if you remember, I wrote in my last
mail a search  class(SearchFilter), it fetchs all of
info.; please mail me your codes.
may be below link can help you:
forum.java.sun.com/thread.jspa

3. I'm not sure because I'm not expert in MSAC and I
can help you a little. in AC you can see windows
authenticate window, but ADAM(App. mode) dosent have
this one. you can find  good info. on this site:
www.microsoft.com/windowsserver2003/
technologies/directory/activedirectory

- unfortunatly, I couldnt import data from AD to
openLDAP, owing to deferences of their schemas.if
anyone know anythings about it plz tell me.