What exactly is impossible?
I can run any software I want on my iPad. No need to jailbreak. Just get Xcode and enjoy the freedom. Who said I need to upload it to the App Store?
(as a side note, these prohibitions seem to have been relaxed in recent years)
I thought that was impossible anyway, given Apple's prohibitions on both GPL code and software runtimes in iOS apps? However I suppose Emacs could be sideloaded onto jailbroken iPads.