I think you are referring to a tweet on March 16th where he said "Btw, the proceeds of any legal victory in the OpenAI case will be donated to charity. I will in no way enrich myself." Not during the trial, not a donation to OpenAI's charity, and obviously not meaningful given his track record of not following through on public statements.
It was official, he amended the lawsuit to codify it, read it for yourself: https://cdn.arstechnica.net/wp-content/uploads/2026/04/Musk-...
Thanks, couldn't find this. This is essentially a proposal to the court about how the case could be resolved though, not a promise, and he only proposed it after the judge denied his original proposal (https://cdn.arstechnica.net/wp-content/uploads/2026/04/Musk-...), which was "give me $134 billion". I think it would have been a little more credible if he had requested this originally.
Even taking it at face value, it's just an idea for the judge to consider, not legally binding for anybody.
Putting it into a filing does not necessarily make it legally binding. I asked ChatGPT and (although it is clearly in the bag for OpenAI ;) it gave more color: https://chatgpt.com/share/6a0baf4a-e408-83ea-a44b-ff68bacb64...