here's the second half...
... ...
But maybe you don't need either of those as I just checked with my Logitech control centre (LLC) v. 3.9.4 that I use with my Logitech M705 USB mouse and Mavericks 10.9.5 and the LCC software is shown as 64-bit.
But besides all that, you may not need any of them as Apple's Mouse pref pain will, or should, provide the option for left or right click button.
It can even switch what my Logitech mouse main click buttons can do, left or right clicking.
The LLC software is only needed for any additional button's options and I don't think the Logitech trackball has any more than the left and right buttons, so you should be all set to go and keep your beloved Logitech trackball working.
EDIT:
PS: Apple seems to like referring to Mouse pref pane buttons as "Primary mouse buttons", and then provide an option to set the setting as "Left" or "Right".
So in their thinking, a right-handed user would select "Left" of course. Honest!!!
To Apple, the "Primary" button = "Click" (left) button. At least for right-hand users.
Confused yet...???
Anyway, I'm sure your Logitech T-BC21 buttons will still work just fine and probably without any need for ant additional LLC software, or just use their most recent whis is 64bit.
- Patrick
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