I don't know if Burst's financials are quite that exotic. A lot of big companies factor their receivables - sell them for XX% to a third party. Seller gets ready cash now, third party makes money on the discount. Extremely common, particularly in inventory-heavy businesses like retail. The third parties then bills (sometimes transparently), or does an arrangement where they oversee receivables.
Or they may simply have taken out a loan.
Or they may simply have taken out a loan.