Is Atari a game developer or game publisher?

[PinoyEngine]

Hello! I am just curious as I am getting hooked to Atari 5200 games. I downloaded a bunch of roms and somehow I am amazed. Anyway, is Atari a game developer or game publisher, because roms' file names like the
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Also, what is Prototype? Is it something like "Alpha/Beta" Version, or its a game developer? or publisher?
Because some roms have file name like:
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[Aeolus Aeneas]

Atari used to be both, then they went out of business. The current Atari, I believe, is just some company that bought the name and is farming out games to other devs to cash in on name recognition.