Before it
Frontier training data was proprietary and undocumented.
The problem
Outsiders could not reproduce large-model training without a comparable corpus.
What it introduced
825 GiB assembled from 22 documented sources, released openly.
Why it matters
It let independent groups train serious models, which is how the open ecosystem started.
What modern models inherit
Open, documented pretraining data as a community resource.
What came next
Pythia, GPT-NeoX and OPT trained on it; later corpora refined its mix.