Ask HN: right way to spin-off from startup

I am the first employee at a now very successful startup. I have been here for a number of years and am a senior engineer in a hands-on 'team lead' role. I have some equity (around 0.2% by my reckoning), am well respected, and on excellent terms with management, investors and rank-and-file.

For the past year or so, my team has been working exclusively on an open-source project that addresses a critical business need, but is also gaining traction outside the company.

I believe the tech is disruptive in it's niche, as do others. I have talked to potential investors, engineers and leaders in the field and have tentative investment, co-founders and influential board member(s) for a new company based on this project.

I would like to offer the CEO of my company a board/advisor role, as well as retain him as a customer. Ideally I would take one or two engineers with me, though I would understand if this is impossible.

Any ideas on how to approach this?