The TOS you noted applies to website use, not the plugin.
So the customers are not redirected to coinsimple's website to make a payment? It may be true, I didn't try it out, but their documentation on github suggests that.
Since Bitcoin Payments for WooCommerce stopped working it is also the only direct to wallet bitcoin payment plugin available. Don't like it? Don't use it or go with BitPay et al which cost more, have onerous KYC requirements to register and are very invasive of your privacy.
That's why I pointed out that he could try my plugin which is (when used in connection with the HD wallet addon) a better alternative to Bitcoin Payments for WooCommerce than using a payment processor. So if he wants to support the development of an alternative that does not limit what you can use it for and does not collect sensible data about you and your customers he should consider trying it out.
edit: even if you don't use it with the HD wallet addon, the customer data will not be shared with third parties and the processing happens in the store.