mornington:
Its by no means a stupid question. Its taken me a while to understand the structure. There is a lot of confusing information out there. But I have to say that most of the misleading comments I have seen have been from advocates of Academies.
Just keep a focus on your question
"what's in it for the private sector companies and individuals who run academies and academy chains.?"
To begin with the legal provisions relating to Academies and to Free Schools are the same. The Government use the term "Free School" to refer to new schools that are set up using the Academy structure, reserving in general the discription "Academy" for schools which have converted to being academies. So everything I write applies to both.
Every Academy, is run, or governed if you will, by an "Academy Trust". The Trust may run a single school, or run a number of schools as a "Multi- Academy Trust" or "Chain"
Each trust is require to be set up as a "not for profit company limited by guarentee" which then applies to the Secretary of State (currently Nick Morgan) for recognition as an educational Charity. Its called an "exempt" charity as they do not, unlike ordinary charities, have to be regulated by the Charity Commission.
An ordinary "for profit " company has shareholders, who own it, elect the Board, and get paid a share of profits as dividends on their shares. If the company goes bust, the most a shareholder can loose is the value of their shares. That is why it is called a Limited Company as the shareholders liability is limited to the value of their share.
A "company not for profit limited by Guarentee" is in law, likewise owned by its "members". These are people (or a company can be a member) who apply to join the Company, and agree, in the event of the company going bust (Being "wound up and found to be insolvent') to contribute a sum of money, usually one pound to pay off debts. So their liability is limited to the size of their guarentee. The members elect the Board.
You will see from this that it follows that who the members are is a rather important point. The member(s) can be commercial, for profit companies. So you can have a trust Board, consisting of employees of the for profit company, which then buys services from the parent company. This is perfectly legal, by the way.
I will give some examples in later posts after you have had a chance to comment on this one.