Could you please stop posting unsubstantive comments to Hacker News?
It's written in my current offer and refers CA Labor Code 2870. I missed that author is in Switzerland.
From what I understand the burden of proof in Lab. Code, § 2872. falls on the employee. If they work on some code in their "spare" time and that code contains a license with the word "Google" in it it would seem the license is a first attempt to establish the burden of proof as opposed to the freedoms one might enjoy writing under the Expat or GPL, for example.