Incidentally, he's currently leading the Large Text Compression Benchmark using a -based compressor called nncp [4] which is based on this work. It learns the transformer-based model as it goes, and the earlier versions didn't use a GPU.
[1] https://bellard.org/libnc/
I kinda understand why he would not release the source code. Perhaps, he's finally decided to monetize some of his coding skills. Maybe in the future, he'll start releasing some of those newer and bigger models to the public given that other big corps like FB have started already doing so (GPT-NeoX and OPT - as mentioned in the sibling comment by infinityio)
Also, he was/is competing for the Hutter Prize with nncp, however he is outside the requirements for the prize: CPU-time, RAM, but most especially that submissions shouldn't require a modern CPU (with AVX-2) or a GPU. Otherwise he could have won it. I suspect it's actually that's the biggest reason he implemented libnc without GPU support initially. He has asked for the rules to be changed to allow AVX2 and I believe they eventually will be. So he won't give away the source for nncp yet, but will have to open source it to receive the prize.
[1] https://textsynth.com/pricing.html
[2] https://help.openai.com/en/articles/6485334-openai-api-prici...
On the other hand, Facebook has recently released the weights for a few sizes of their OPT model [2]. I haven't tried it, but that might be worth looking into, because they claim that their model is comparable to Davinci
Note that for CPU inference you will be unable to use float16 datatypes, otherwise it might error out
[0] https://huggingface.co/EleutherAI/gpt-j-6B [1] https://huggingface.co/EleutherAI/gpt-neox-20b [2] https://huggingface.co/facebook/opt-66b