GPT-3, as it is more commonly known, was developed by OpenAI, an artificial-intelligence (AI) laboratory based in San Francisco, and which Mr Musk helped found.

1. 最后这一部分 which Mr Musk helped found 是 OpenAI 的非限制性定语从句，而 and 表明它与前一个成分并列。那么，an artificial-intelligence (AI) laboratory based in San Francisco，也应按照定语分析，相当于一个非限制性定语从句：which is an artificial-intelligence (AI) laboratory based in San Francisco。

2. 这样处理的好处是：两个都是并列的定语，由 and 连接，避免了一个是同位语、一个是定语从句的尴尬。and 原本就有的，不能随意删除。

3. GPT-3, as it is more commonly known, was developed by OpenAI, (which is) an artificial-intelligence (AI) laboratory based in San Francisco, and which Mr Musk helped found.

翻译：众所周知，GPT-3 是由 OpenAI 开发的，它是位于旧金山的一个人工智能实验室，也是马斯克帮助创建的。