If effect, kind of.
The money being invested does not go directly to investors.
It goes to the cost of R&D, which in turn increases the value of openai shares, then the early investors can sell those shares to realize those gains.
The difference between that and a ponzi is that the investment creates value which is reflected in the share price.
No value is created in a Ponzi scheme.
The actual dollar worth of the value generated is what people speculate on.