Selling bandwidth: is it legal?
The services themselves can be used legally. What matters is not the service but your own internet contract – and the question of who owns the network the Pi sits in.
Point 1: your ISP's terms of service
Some providers explicitly forbid making your connection available to third parties or routing third-party traffic over it. Wordings such as “resale”, “commercial use” or “transfer to third parties” are the clauses that matter.
Reading your own contract takes five minutes and is the only way to settle this for your tariff. General statements online do not help, because the clauses differ between providers and between tariffs.
What happens if you are in breach Breaching the terms is usually a contractual matter rather than a criminal one. Typical consequences range from a warning to the provider terminating the connection.
Point 2: networks that are not yours
This is where the latitude ends On networks that are not yours – student halls, your employer, a shared flat on one line, a hotel – you need explicit permission from whoever runs it. Without it you are routing third-party traffic over a line somebody else is answerable for.
This is where a contractual question quickly becomes something larger. Quietly routing third-party traffic through a corporate network can carry serious consequences depending on your employment and internal policy. Ask first.
What technically runs over your line
Requests from the provider's business customers run over your IP address – typically market research, price comparison, ad verification and availability checks. The providers state that they vet their customers and targets in advance.
You cannot verify this As a user you have no visibility into what traffic actually passes over your connection. That residual risk is part of the decision. Anyone unwilling to carry it should not use these services – an entirely legitimate choice.
And the earnings?
Income from these services is income. How it should be treated depends on the amount, on your wider situation and on how it is classified in your case. There is no blanket answer, and when in doubt it belongs in your tax return or with a tax adviser.
What this page is and is not A private guide with a technical focus. Not legal advice, not tax advice, no income guarantee. For concrete legal or tax questions there is no substitute for professional advice.