IIRC you can install unsigned extensions in the dev and nightly as well as unbranded versions of firefox (usually the last option means compiling it yourself).
Mozilla is, to some extend understandably, concerned with the image of Firefox and patrolling what Addons are available in the store is part of that. Apple does the very same thing.
Mozilla is, to some extend understandably, concerned with the image of Firefox and patrolling what Addons are available in the store is part of that. Apple does the very same thing.