I don't think "design" is correct word: organized, managed, or ran perhaps.
> The FreeBSD Project is run by FreeBSD committers, or developers who have direct commit access to the master Git repository.[1] The FreeBSD Core Team exists to provide direction and is responsible for setting goals for the FreeBSD Project and to provide mediation in the event of disputes, and also takes the final decision in case of disagreement between individuals and teams involved in the project.[2]
* https://en.wikipedia.org/wiki/FreeBSD_Core_Team
There is no BDFL, à la Linux or formerly Python: it's a 'board of directors'. Decisions are mostly dispute / policy-focused, and less technical for a particular bit of code.