It's been a long time since I've messed with iOS cracking and such, but I know for certain it is possible to dump apps, as seen above. The system that I used could sideload apps that didn't have protection, which I'm betting a free app from years ago doesn't have. I checked more current pirate sources and the Sonic 20th Anniversary app wasn't there, the norm for free apps. It seems the app is publicly unavailable right now.
The ipa file should be on your computer in your iTunes folder if you've backed the app up, so you can Dropbox/MEGA it for yourself. I personally wouldn't release it without making sure any personal identifying information is stripped out, such as iTunes account details used to trace leaks, but that's your risk if you want. Having the ipa around would make sure that it can be cracked/released in the future, even if it's removed from the app store completely (it has happened before). If does need to be cracked, a lot of the cracked app stores have tools available for it but I've no clue where to begin on actually cracking apps.
A side note: A lot of these tools only work on older iOS versions, and older versions of iOS can always be jailbroken,. The versions I used were iOS4-6, and these still can be installed on older devices such as the iPod Touch Gen 4. Very useful in dumping apps if newer devices give you trouble.
(I seriously typed in "Sonic The Sketchhog ipa" in Google and after 5 seconds found this... Are people just not searching in the right places or I'm really good at finding scarce files?)
