Er, dude, you do. A Free license doesn't mean there is no license. If you obtain libmysql.so and use it in any way, you have to respect the license or you're in breach of copyright law.
The fact that free (re)distribution is allowed by the license does not mean that the use of it in any way is not restricted.
> this interpretation followed to its logical conclusion makes huge swaths of the free software ecosystem illegal
That might well be. Free licenses are abused every day, as people don't really know what this or that license requires. They even routinely strip copyright statements on MIT/BSD code, which is literally the only thing one is not supposed to do. But just because people get away with speeding over the limit on most days, it doesn't mean that the speed limit is not legally enforceable.