[belorn]

The kind of speech that is limited would be things like publishing malware, or doing illegal advertisement. No advertisement to kids, no alcohol, no tobacco, no prescription medicine, no guns, and no fraudulent messages.

Taxes is also pretty much defined by the expectation of compensation. If a speaker talks on a conferences and get paid to do so, they will need to pay taxes. They have as much open free speech they can get, but they are not free to demand compensation for it without paying taxes.