"What do you mean free and additional?"
Compared with other command equipment, it means that you don't have to go out and spend $300 to have a remote that will control the Lionel LionChief or LionChief Plus loco you just purchased in command mode.
"But we all know that that type of compatibility is not what folks on this forum call compatibility.
"
We do? Now you speak for the whole forum? I responded as I did precisely because one could not be sure what the original poster meant by compatibility. I was trying to be informative and helpful.
"You sound like a used car salesman, not trying to offend any car salesman on this forum"
Seriously, you expect a used car salesman to read that and not be offended? No one, least of all me, wishes to know your opinion on what I sound like. I can assure you that my daily work is entirely reputable, as is that of most used car salesmen and saleswomen 
.
I don't waste my time trying to discredit the opinions of others. Or questioning the character of others, be they car salesmen or otherwise.
And yes, DCS and Legacy/TMCC locos are compatible in the sense I discussed. The original poster did not ask "can I operate a LionChief loco with my TMCC cab-1?" He asked whether they were compatible. Not inter-operable.
