The negative effect is that you have to bring the lawyers back in, and they tend to take an extremely conservative position on what might be litigated as offering “Redis-as-a-service”.

Would they? My experience is the lawyers sign off when software is being chosen, but then they aren't consulted again.

After that, it is just updating version numbers. Lawyers don't sign off on version upgrades, why would I bring this to them?

Many legal departments cannot afford nuance when a newsworthy license change occurs. The kneejerk reaction is to switch away to mitigate any business risk.

I doubt having lawyers review your usage is more expensive than spending hundreds of hours of dev time to migrate.

Our lawyers looked at SSPL since we do host software for customers and it does use Redis and went "Eh, this is as clear as mud." so Valkey it is!