Tooltips were one of the last things that we did in GC1 and it will probably be the same here. There's so much that changes on the interface from the beginning of the beta until the release version that makes it easier to wait until closer to release to do tooltips.
That being said, the Society team is currently working on getting tooltips into their alpha of Society. Once they have it working, I could easily plug it into GC2. If one or more of you would like to volunteer to work on the tooltips data file for GC2, it would save us a lot of time. All you need is a version of DesktopX (even the free version will work) and a text editor.
This is what you would do:
1) Run DesktopX. When the little popup comes up, choose Create so that it starts in build mode.
2) Double click on one of the dxpacks from the GC2 screens folder to open it.
3) Right click on the DesktopX icon and choose List Objects. This lists all the objects in the screen.
4) Apart from fonts, tabs, and listboxentries, which are all just for information, you can make a tooltip for any of the objects in the dxpack. I suggest sticking with the static strings and buttons for tooltips. You will not be actually editing the dxpack. You just need to be get the OBJIDs for the controls that need tooltips.
5) Create a text file with the same name as the dxpack and give it the extension .tip and open it in a text editor. This is the format for the tooltip tables:
[TABLEALIAS MainWnd]
[TurnButton] Hit this button to advance to the next turn
[TABLEEND]
The word that comes after the keyword TABLEALIAS is the name of the dxpack without the extension. The OBJID for the control you are assigning the tooltip to goes in [], like [TurnButton]. [TABLELEND] closes the table and if you forget it, the parser will be unhappy and quite possibly mess up all the rest of the tables it reads in too.
If you're interested in helping, use this forum and #galciv on irc.stardock.net to coordinate your efforts. If you're not, no big deal, but thanks a bunch if you are.