This whole debacle arose from unhappy contributors of the Steam Translation Server, a volunteer effort to help localize Steam (and some of its games) into many other languages.

STS started some time in late 2009/early 2010, when Valve was a significantly smaller company than it is now. This was before Dota 2, CSGO, F2P TF2, and before a significant amount of third party devs started supporting Steam. At the time it was considered acceptable for Valve to create a volunteer translation team, because localization is a slow and costly process. At the same time, lots of these early volunteers believed that contributing to STS would be a stepping stone towards receiving legitimate jobs on Valve's localization team. One Valve employee even went as far to hint that STS volunteers could later become Valve localization employees.

Fast forward 6 years. Valve is now a multibillion dollar company which can very easily afford to localize its own products, but they are still relying on a volunteer-only service... and many of these volunteers have been providing their services for over half a decade. At this point it's not volunteer work so much as it is a never-ending unpaid internship. To my knowledge no one has ever advanced past STS volunteer work to become a proper Valve employee, which is why the Spanish STS community was in an uproar over the carrot-dangling going on. I'm not sure what transpired beyond this, but some STS admins and moderators resigned/were removed, and a Valve employee which objected to this behavior was fired.