FMF and Commissions

I have a client that is hiring a sales agent in a foreign country.  This agent's territory will likely include contracts subject to FMF rules, sales will be direct commercial.  This particular client compensates all of their sales agents with a commission plan.  I've never worked with FMF before - it appears that commissions are allowed, but they have to be disclosed, they cannot be in violation of Anti-Kickback regulations, and it appears that commissions may need to be split out and paid by the Purchaser's national funds.

My questions:

1. I'd like to wrap my head around this better.  What is the purpose of the FMF rules on commissions/contingent fees?

2. What does the last provision (paid by Purchaser's national funds) mean?

3. Where can I find the source document that discusses FMF commission requirements from a contractor's perspective?

Thanks in advance!

Patrick