Created a Sprint version of amoamare's hack. Push the apk to /system/app and you should be good to go. We can haz tether people.
Here's the code I changed:
.method protected isEntitlementSuccess()Z
Only if it's installed I guess. This is how to disable it. Anryl's ROM has it install and turned on by default.
That's good news. I've been looking for a way to enable it in the first place on 6.5. It doesn't work at all on 21500....