Complex sentence: Valve places a strong emphasis on the independent developer as well as user developed content demonstrable through Valve's Steam Workshop platform, a feature of Steam (Valve's gaming ecosystem featuring hundreds of millions of active users).
Split into simpler sentences: Valve places a strong emphasis on the independent developer as well as user developed content. It can be seen with Valve's Steam Workshop platform, a feature of Steam (Valve's gaming ecosystem featuring hundreds of millions of active signed up users).