I'm not saying you shouldn't use these licenses or contribute code to permissive license projects. I use permissive and copy-left licenses, depending on the situation. In any case, you should know what you are granting.
Redis did say that they would never relicense core from BSD, and I'm sure many contributors trusted their word in his faith. I am not a lawyer and have no idea how binding corporate blog posts are, but the BSD license itself allows them to do this.