No jailbreak required - just a backup of your older version Lemur .ipa.
http://www.i-funbox.com/
Free, as in beer.
As a bonus, you get to keep the blue file icon - which hasn't exhibited any bugs yet should should be safe to keep!
[Edit: USB Tunnel]
The USB Tunnel feature looks like a possible candidate for getting OSC (and possibly MIDI) out through the USB port (std cable). That may require a jailbreak - suffice to say I haven't got it working on my non-jailbroken iPad2 so far. That is as likely due to my incompetence as any requirement for root, so worth taking a crack at.