[msbarnett]

Apple licensed Rosetta on a per-install basis from Transitive Corp.

Then, IBM bought Transitive and discontinued the PPC->Intel translation engine.

Apple did not have the option to continue shipping Rosetta, because IBM axed the team that would have had to update it for Lion.

[vor_]

That very well may have been a factor. However, Apple engineers have publicly stated that for them to continue supporting PowerPC Macs would have required developing and shipping system APIs targeting a processor they hadn't sold in over half a decade. I think Rosetta's number was up regardless.

[msbarnett]

I think that would only make sense if they wanted to allow people writing new software targeting the PPC to be written, using new APIs.

To support only applications that existed prior to the Intel switch, they wouldn't need to back-port new APIs.