(Didn't you answer your own q?) If the contractor is doing unlicensed work, a complaint can be filed against the contractor with DBPR. (Note however that for a 1st offence only a notice is issued against the contractor, the fines up to $10K + investigative costs, as far as I can tell from Florida's 489.13 statute.) The Florida bar actually lists a bunch more of these possible consequence for the unlicensed contractor:
There are at least eight possible legal consequences that can result from construction activities by an unlicensed contracting entity, each of which is described herein.
- Loss of contractor’s contract rights (F.S. §§489.128 and 489.532).
- Loss of lien and bond rights (F.S. §713.02(7)).
- Treble damages (F.S. §768.0425).
- Damages for violation of building code (F.S. §553.84).
- Administrative sanctions (F.S. §§455.228 and 489.13).
- Criminal penalties (F.S. §489.127(2)).
- Possible action for “disgorgement” (per case law).
- Cause of action for “unfair trade practice” (F.S. §501.204).
For example, pursuant to §489.127(2), any violation of the grounds for disciplinary action under subsection (1), which includes advertising the availability to engage in the business or act in the capacity of a contractor without being duly registered or certified or having a certificate of authority, is punishable as a misdemeanor of the first degree.
In addition, any unlicensed person who commits a violation of subsection (1) after having been previously found guilty of such violation commits a felony of the third degree, and any unlicensed person who commits a violation of subsection (1) during the existence of a state of emergency declared by executive order of the governor commits a felony of the third degree.
The page actually discusses some exceptions too, but those mostly apply to single-family residences (more unlicensed work is possible there).
F.S. §553.84 actually says:
553.84 Statutory civil action.—Notwithstanding any other remedies available, any person or party, in an individual capacity or on behalf of a class of persons or parties, damaged as a result of a violation of this part or the Florida Building Code, has a cause of action in any court of competent jurisdiction against the person or party who committed the violation; however, if the person or party obtains the required building permits and any local government or public agency with authority to enforce the Florida Building Code approves the plans, if the construction project passes all required inspections under the code, and if there is no personal injury or damage to property other than the property that is the subject of the permits, plans, and inspections, this section does not apply unless the person or party knew or should have known that the violation existed.
(Somewhat of an aside, a supplier of materials, e.g. of defective concrete, was held not liable under that section. Only the actual contractor doing work is potentially liable under §553.84.)
A general contractor can also be fined for hiring unlicensed sub-contractors.
a general contractor can face licensure issues, a cease and desist notice from the Department of Business and Professional Regulation (DBPR), and fines up to $5,000 for knowingly hiring an unlicensed contractor. Section 455.228(1)-(2),
The Supreme Court of Florida held (in 2013 -- SC10-1892) that the law intentionally puts less onus on the party doing the hiring than on the (sub-)contractor themselves.
As far as the customer is concerned, it might not be criminal for the customer/board to hire an unlicensed contractor, but if things go wrong and someone gets hurt (e.g.) by that embankment collapsing, the board can be held (partially) responsible in a civil negligence trial; see contributory negligence for the general principle in common law.
Furthermore, due the Slavin Doctrine, the contractor itself may be completely off the hook for damages to 3rd parties, if the faults in their work are probably apparent to a customer excercising resonable care. Note that that doesn't mean the customer actually discovered the defects:
The Third DCA explained the reasoning of the Slavin Doctrine as a presumption that the owner had conducted a “reasonably careful inspection” of the contractor’s work prior to accepting it as completed and that the owner of its work accepted the project as complete while adopting the defects and negligence of the contractor’s work as his own. The Court embarked on a lengthy analysis of the test for “patency” of a defect, which is whether or not the dangerousness of the condition was obvious had the owner exercised reasonable care, and not whether or not the condition was merely obvious to the owner. The Court was careful to note that the test for patency relates to what the owner “could have discovered” and not what the owner actually discovered, had the owner performed a reasonably careful inspection.
(Some states other than Florida subscribe to the "foreseeability doctrine" which doesn't completely absolve contractors in such a scenario.)