@Sherry -
Because everything is the same except the product.
Er, no: BackupBuddy has always been licensed under GPL. Thesis wasn't.

It’s a product built specifically for WordPress, built with WordPress and PHP code. And was put up for sale to the general public. I don’t understand your confusion.
And I don't understand how you can even attempt to compare the two:

1) Again: they're PHP code, so everyone to whom that code is distributed has the source code.
2) Chris Pearson potentially violated WordPress' license by incorporating core WordPress code into Thesis, and then distributing that code under a restrictive license. BackupBuddy does not incorporate core WordPress code - and in any case, is already licensed as GPL.
3) Neither Thesis nor BackupBuddy has to provide anything to anyone to whom the code itself has not been distributed.

Chris Pearson was of the same mind – that he didn’t have to provide the source code to people who didn’t purchase it. Until his very public debate with Matt Mullenweg over it and then eventually conceded.
Chris Pearson's contention (and one in which he was, legally speaking, correct) was that WordPress' GPL does not in any way compel him to license Thesis under GPL, unless actual WordPress code were incorporated into Thesis. (Of course, once it was discovered that core WordPress code had, in fact, been incorporated into Thesis, the argument was essentially moot.)

Still: you've not demonstrated how the Thesis situation in any way applies here.