We're on ISBoxer 40 now, you don't need a beta of 38 to enable this feature, no.

If you want to enable this option, it's built into the broadcasting toggle. First make sure
Video FX works for you, because it's the same thing except the cursor one is centered on the cursor when you flip on broadcasting. Most people prefer normal Video FX. (more on that below)
So.. to try this out..
1. In the top left pane in ISBoxer, under Key Maps, select "Always On" (or "Control" if you are playing WoW)
2. In the bottom left pane, under Mapped Keys, expand "Activate Repeat" so under it you see Steps, 1 and 2
3. Select the 1 under Steps so that to the right you see Actions, and then some Actions under it
4. The second Action down is, by default, "Repeater mouse On keyboard On -> self". Select this Action and its options will come up on the right
5. The "Cursor-based Video FX" box is the "Cursor feeds" that you are looking for.
5a. Check the "Video FX" box so that it will turn On
5b. Check the "Video source size" box and give it a size, this will be the size of the Source around the cursor, in one of the Repeater Target windows (noting that if Repeater is sending to more than one Target, the Source window will be completely random as you move the mouse...)
5c. Check the "Video output size" box and give it a size, this will be the size of the Viewer around the cursor, in the current window. The source and viewer sizes don't need to match, so you can zoom in or out by adjusting them.
5d. Check the "Opacity" box if you want to make the view partially see-through. 255 is solid, 0 is transparent.
6. Export to Inner Space to activate any changes you make
Then when you hit Shift+Alt+R, this would turn on the cursor-based view.
This option is more useful when you are sending directly to one other window, because of the note on 5b: if it's sending to more than one window, both of those windows want to be the Video FX Source for the cursor, and it will change as you move the mouse. But, in most cases when you are sending directly to one other window, a static Video FX view is more convenient.