"Active" in all electronics means it has its own power supply, an amplifier built-in to boost the signal, vs anything Passive, the opposite.
But you do want to make sure when hooked up individually, they both work. This should work if both of your devices are stereo, but if you soundbar expects a surround signal, that may not be compatible with the wireless. TV audio setting would have something like pcm/surround.
Before buying another splitter - do your soundbar and wireless headphones work when connected directly to the TV?
As for "active splitter": This is a device having its own power supply, and "amplifying" the input signal, something like these. As you can see, they don't cost $5.99
Wouldnt an optical splitter need to be active to effectivly work??
With copper you just Y the connection and it works. Optical works by adjusting the angle of the light in the cable/tube. Now someone correct me if I am wrong but I would imagine that you could not just us a mirror or other means to multiply the optical signal. Thus to split it you have to have an adapter that takes the input light signal, converts it to electrical signals and then converts that signal back to optical and pushes out both of the outputs simultanously.