Schulman writes:

I shared the following note with my OpenAI colleagues today: 

I've made the difficult decision to leave OpenAI. This choice stems from my desire to deepen my focus on AI alignment, and to start a new chapter of my career where I can return to hands-on technical work. I've decided to pursue this goal at Anthropic, where I believe I can gain new perspectives and do research alongside people deeply engaged with the topics I'm most interested in. To be clear, I'm not leaving due to lack of support for alignment research at OpenAI. On the contrary, company leaders have been very committed to investing in this area. My decision is a personal one, based on how I want to focus my efforts in the next phase of my career.

(statement continues on X, Altman responds here)

TechCrunch notes that only three of the eleven original founders of OpenAI remain at the company. 

Additionally, The Information reports:

Greg Brockman, OpenAI's president and one of 11 cofounders of the artificial intelligence firm, is taking an extended leave of absence.

(I figured that there should be at least one post about this on LW where people can add information as more comes in, saw that no one has made one yet, and wrote this one up)

Update 1: Greg Brockman posts on X:

I’m taking a sabbatical through end of year. First time to relax since co-founding OpenAI 9 years ago. The mission is far from complete; we still have a safe AGI to build.