That is not correct; assuming you are not using an employer’s equipment on employer’s time, and/or working on what the employer pays you to do for them or are working on something that is competing and a few other reasonable caveats.
As far as I was told, this is not enough, you have to add extra legal care, even more if you are on an 'executive' type job contract, and you have to double that if there is "too much" connection/"look-a-like", between the software at work and the open source software you contribute to "at home".
On an french executive like contract, the boundary between "at home" and "at work" is very, very blurry.
It’s actually quite reasonable and logical.
https://french-business-law.com/french-legislation-art/artic...