Prozbul on Money in a Gemach

I manage a Gemach fund from an amount donated from a benefactor's estate. The money is solely the donation of the benefactor who wrote in the will to establish a Gemach fund from part of the estate. Should the Gemach be included in the Prozbul, and if so, how?

Debts to a Gemach fund, if there are no private deposits in the fund and all the money is dedicated to the Gemach, are not annulled in the Shemitah year.

In the Gemara (Bava Kamma 37a), it is explained that orphans do not require a Prozbul because the court is considered the father of orphans, and it is as if their debts are entrusted to the court and are not annulled. The Rashba and Meiri write there that similarly with charity debts, the court is their father, and it is considered that the debts are entrusted to the court and are not annulled. The Shulchan Aruch (Choshen Mishpat 67:28) also rules that charity debts are not annulled. However, the Levush (there on the words of the Shulchan Aruch) writes that the reason charity is not annulled is because it is written "do not press your neighbor and your brother," and charity is not considered "neighbor" and "brother." The difference between the two reasons is in a case where the charity fund has a debt to others, [such as when a person deposits money in a Gemach fund and the responsibility is on the Gemach fund], according to the reason given by the Rishonim that the court is the father of charity, in this case where the charity fund owes others, the debt is annulled, as this reason applies only to debts owed to the charity fund - for the benefit of the charity fund, but the debts of the charity fund to others are not entrusted to the court. However, according to the reason given by the Levush that a charity fund is not considered "neighbor" and "brother," it is not annulled, and just as a debt to charity is not annulled, so there is no prohibition to claim from charity. (Azmera Leshimcha, Laws of Shemitah).