Found my docs:
PR 1.2 is a must

If you would like to give your video from n900 to the skype person (I will need to assume the other party is using skype 4.2).

If the other party does not have a webcam enabled -> there is a possibility that your n900 skype will not have the video option enabled.

So I use this trick to make it work.

Option 1
1. Ask the other party to use "screen sharing"
2. Right click on your skypename -> Share Your Screen -> Share Selection
3. Click on Start Sharing.

4. Then your n900 will ring -> Pick up the phone
and you will see the camera option will "appears" on your n900,
5. Click on the camera to send your video to your friend
6. Stop Screen sharing (from your friend)

then you will be able to send video from your n900 to your friend.

Option 2:
1. Establish a skype call to the person (a normal skype call)
2. Ask your Friend to use the screen sharing
Right click on your skypename -> Share Your Screen -> Share Selection
3. Click on Start Sharing.
4. Your N900 screen will change to allow video call.
5. start the camera on your n900
6. stop the sharing


PS: DO NOT try to use share your screen -> Full Screen because the call will be aborted.

Have fun for video calling :-)