It means that anyone can make content related to Serial Experiments Lain like animations, games, mangas and stuff like that without having a proper copyright permission for it.
"20 years may have passed since the premiere of the seminal Serial Experiments Lain, but fans haven’t stopped loving Lain – not one bit, especially as the series only gets more and more relevant in today’s world. Faced with such fan support, NBC Universal has taken the unprecedented decision to hand over their intellectual property almost entirely to fans – making Social Experiments Lain, as they describe it, ‘open source’ under the moniker Time To Live."
You can use her likeness for pretty much anything now, which is cool. Given how the internet works it doesn't change a whole lot on a practical level, but it legitimizes a lot of things that were previously gray.
