The rumour originates from Rixstep, and since I had never heard of these guys before, I pretty much assumed from the start that it was a bunch of nonsense. When I actually came to read the story they posted, it became even more apparent: this was a load of nonsense.
"Developers planning on marketing software for 10.7 will submit their products to the App Store as iPhone and now iPad developers have already done," the rumour reads, "10.7 will have kernel support for ('insistence on') binaries signed with Apple's root certificate. No software will be able to run on Mac OS X 10.7 without being approved and signed by Apple, Inc."
The rumour fell apart right there, as 9TO5Mac notes, since Mac OS X's kernel already has support for signed binaries (more here), and in fact, is already using this technology. You can spot signed binaries on Mac OS X quite easily: applications that ask you keychain access after being updated are not signed, and those that do not ask, are signed.
In any case, lousy rumour or no, the prospect of iPhone-style application control ever coming to Mac OS X is not a pleasant one. As such, Mac developer Fernando Valente decided to email Steve Jos at his usual address. "There's a rumour saying there will be a Mac App Store and no software without authorisation from Apple will run on Mac OS X," he asks, "Is that true?"
"Steve Jobs' response" (I'm assuming a number of Apple people monitor this address) was as clear and to the point as can be. "Nope."
Good. Mac OS X is a great operating system, and nobody wants it ruined by totalitarian and arbitrary App Store management.