Beyond their own contributions, Redis Labs are presumably benefiting from the work of outside volunteers on said free software project; and you do not seem to be claiming (yet) that Redis Labs gives anything back to these volunteers.

This comment is baffling. I cannot make any sense of it, unless you think that somehow, the progress of the Redis core open-source project does not benefit anybody except Redis Labs. If you don't hold that nonsensical belief, then it is obvious that Redis Labs gives back in kind to contributors to their projects -- the Free core Redis project, as well as the non-Free plugins (which are still available for most uses, at no charge and with malleable source code).

I fail to see any hypocrisy on Redis Labs' side here, nor mistreatment of volunteers.