Just thought I'd post this here so people don't get surprised by it later like I was. It's certainly not spelled out on the website.
The only way to get a license to use Sencha Charts for commercial use is to buy the Sencha Complete package, which starts at $995 per developer.
It's good to know in advance in case it prices you out of even bothering to look at it. It did for us, and I'm glad I found it out before wasting too much time learning how to use it.