I was trying to connect to another broker, but only IB is available.

We currently only have a broker interface for IB implemented. What broker are you looking to connect to?

My strategy needs a commission-free broker (like InteractiveBroker Lite, but it seems to me that it doesn't allow API connection), I still haven't choose which broker to use because I am not sure about the backtest results, they are what I was looking for, but they seem too good to be true...

What about Thinkorswim? Does it connect to place automated trades with Thinkorswim(TDAmeritrade)?

Currently no, but there seems to be a good demand for that to be the next broker that we focus on implementing!