Laz's questions

I'm looking for a good open-source alternative to active directory that can handle:

• Authorization/Authentication
• Group Policy
• Replication and Trust Monitoring

In addition, are there any consolidated systems out there that handle these responsibilities?

Edit: Since a lot have asked for more details, I am trying to offer a service setting up an infrastructure for organizations, hardware/software setups, right now I am looking at a Linux stack, both desktops and servers, however a hybrid stack is possible, and I am investigating alternatives.

I am trying to get some guidance on working solutions for corporate portal setups? What hardware and software were involved in such a setup?

Both proprietary and non-proprietary solutions would be useful.

If you have seen such a setup in use, how has it worked out? What were the advantages/disadvantages?

Background: My company operates in different locations and has hundreds to over a thousand users at some locations. It has both mobile and office workers.

To expand on my question, requirements are access to various applications the company hosts, updates/news sections to disseminate information, authentication API that other applications can utilize through possibly some kind of web service.