"Clients in Professional Free Activity" ... What does that mean ???
I believe it means companies who paid for his services as an independent consultant. Free meaning independent, not gratis. It sounds like an awkward translation of some Italian idiom.
EDIT:
The Italian wikipedia entry on consulenza (consultant) leads to "libero professionisti" as the source phrase, which Google translates as "freelancers." "Libero" is translated as "free" by the same source. The phrase "consulenti libero professionisti" has 534,000 hits on Google.
So OB's poor translation, "professional free activity," is probably from "attività professionale libera," or "activities as a freelance professional." There is no reason to think those companies got those consulting activities without payment.
Italian wikipedia:
I consulenti esterni che non provengono da società di consulenza, ma operano come libero professionisti, vengono detti freelance.
Google translation:
External consultants who do not come from consulting companies, but work as freelancers, are called freelancers.
M.