Open-Transactions democratizes financial and monetary actions. You can use it for issuing currencies/stock, paying dividends, creating asset accounts, sending/receiving digital cash, writing/depositing cheques, cashier's cheques, creating basket currencies, trading on markets, scripting custom agreements, recurring payments, escrow, etc. Open-Transactions uses strong crypto. The balances are unchangeable (even by a malicious server.) The receipt history is destructible. The transactions are unforgeable. The cash is unlinkable. The cheques are non-repudiable. Etc.
I propose you to add a compilation of protobuf to avoid installing it from Debian Sid which, as far as I can tell, is not straightforward.