It was called MPEG2 Layer III, right? And the licensing around mp3 is why many Linux distributions didn't offer mp3 in the default install, without adding "non-free" repositories.
We also saw open standards emerge, like Ogg Vorbis and FLAC (although neither were widely adopted by hardware vendors compared to Apple's AAC/ALAC)
It is not "Apple's AAC". Apple did not have any part in the development of AAC. It was actually developed by Fraunhofer as a successor to their MP3 encoding.
IIRC, MP3 was based on the audio component of the first "MPEG" standard (the one used for Video CDs) rather than MPEG2 (the one used for DVDs, amongst other things), which would make it "MPEG Layer III".
We also saw open standards emerge, like Ogg Vorbis and FLAC (although neither were widely adopted by hardware vendors compared to Apple's AAC/ALAC)