1. It attracts the world's best academic talent, who deeply want their work shared. AI experts can join any company, so ones which commit to open AI have a huge advantage.
2. Having armies of SWEs contributing millions of free labor hours to test/fix/improve/expand your stuff is incredible.
3. The industry standardizes around their tech, driving down costs and dramatically improving compatibility/extensibility.
4. It creates immense goodwill with basically everyone.
5. Having open AI doesn't hurt their core business. If you're an AI company, giving away your only product isn't tenable (so far).
If Meta's 405B model surpasses GPT-4 and Claude Opus as they expect, they release it for free, and (predictably) nothing awful happens -- just incredible unlocks for regular people like Llama 2 -- it'll make much of the industry look like complete clowns. Hiding their models with some pretext about safety, the alarmist alignment rhetoric, will crumble. Like...no, you zealously guard your models because you want to make money, and that's fine. But using some holier-than-thou "it's for your own good" public gaslighting is wildly inappropriate, paternalistic, and condescending.
The 405B model will be an enormous middle finger to companies who literally won't even tell you how big their models are (because "safety", I guess). Here's a model better than all of yours, it's open for everyone to benefit from, and it didn't end the world. So go &%$# yourselves.