Is this legal? I was reading upon where the border is between being a non-professional and professional traders. But it only says that you cannot have more than 2 data streams of live data. But how about if you have a ThinkOrSwim account, and perhaps 1 at ETrade and 1 at your local bank? Are there limits to this? Can a non-professional have 30 accounts and still being non-proffesional?

I'm not 100% sure what you asking but assuming you are asking about CME Data Fees, and their definition of Pro vs Non-Pro maybe this may help

https://www.cmegroup.com/market-data/distributor/files/exhibit-a-to-schedule-4-non-pro-self-cert-form.pdf

The data stream part is in part (h)

The Non-Professional Subscriber’s Access to Information must only
(h) be via a maximum of two trading terminals per Distributor, permissioned for Real-Time Information and capable of routing orders to the CME Globex Platform (an “Order Routing Device”).

Notice the use of 'per Distributor'. I think your example of ThinkOrSwim + ETrade + local bank would be 3 different distributor's.

You may need to check with your broker for their requirements also.
A while back I applied for an account with a broker and they refused to allow me to trade as a 'non-professional' because of my profiles on Linkedin, Twitter, etc.

I had some information saying I was a trader.
(never mentioned professional in the posts)
They claimed those posts meant I was a professional.
WTH?
Weird that they would check my Linkedin and Twitter profiles.

I am not a professional so I went with another broker.