My company is a passport advantage customer and we purchase our licenses and maintenance under a CEO contract. This allows me to install 6.0.x as well 6.5.
Correct. If you are active under maintenance you are entitled to all releases of the product.
Now I have plans to upgrade 6. Do I upgrade to 6.0.x or 6.5 on my mailserver servers or not?
That would depend on what you want to accomplish. I assume you are currently on a R5.x release. Moving to either release within the ND6 code stream will give you thousand of benefits. If you are asking specifically what D6.5 gives you over D6.0.3.... here is a list of what is new:
http://www-10.lotus.com/ldd/today.nsf/a2535b4ba6b4d13f85256c59006bd67d/38ce21a6f60cc20885256da40049eef9?OpenDocument
Can I upgrade a server to 6.5 and then have my 200 sametime users work with the 6.5 client and everybody else with a 6.0.3 client?
Yes you can. Remeber to also upgrade the 6.5 users mail templates to get the new Instant Messaging functions. Also check out the new Domino Web Access!
Do I need those websphere licenses or can I use the 6.5 server and client and get away without have to purchase any websphere licenses? Where does that websphere functionality really come in play?
If you are you are talking about the limited time offer of 20 free WebSphere Portal licenses, then the answer is that you do not NEED to use these at all. They are being offered to you so that you can start to learn about WebSphere Portal.
If you are talking about the included license for WebSphere Application Server (WAS) included with ND6, that is so that you can develop servletts which execute on WAS and access Domino data via the Domino 6 JSP tags.
I hope this helps..
Alan - IBM