Do I need to purchase the Efinity tool to use and program the Hexberry-V board? Absolutely not: the tool is called 
and is provided by Efinix for free (visit this link for more information).
Can I create an SoC (system on chip) with this board? Of course: you can insert the processor you want, even if this FPGA natively allows you to use a 32 bits Risc-V softcore (SAPPHIRE VexRiscv with RISCV32I ISA), and the manufacturer Efinix provides an IDE based on the Elipse tool with which to develop the firmware after having structured the circuit solution.
I am worried about possible theft/counterfeiting or corruption of my bistream. Does Hexberry take any measures to eliminate this problem? Absolutely yes. The flash memory which usually contains the bitstream which is then transferred to the FPGA has been physically inserted into the FPGA, making the system safe and incorruptible against both theft/counterfeiting and corruption.
Can I have additional features with Hexberry to increase the Anti-cloning and Anti-piracy of my digital solution? HEXBERRY-V has been equipped with a "Crypto Authenticator" IC for holding secrecy keys (Random Challenge-response methods available), making the effort of potential hackers enormous to circumvent the system.
Where can I find the documentation for this project? The Hexberry-V-20Q100 project was released under the OPEN Hardware CERN-OHL-S (strongly reciprocal) license. Under these conditions (it is important to read the license, as the use of the documentation implies implicit acceptance of the license), the entire documentation is entirely available on our REPO.
What can Hexberry-V be used for? Certainly to neophytes in the world of FPGAs (students and Makers), who can try to create their Digital project (replacing discrete logical components or composing a calculation system with a 32-bit microprocessor surrounded by different peripherals each time, without spending a lot of money for both the board and development tools. It can also be suitable for designers who need to integrate a low-cost, low-power, small-size FPGA solution into their design.
Do I have to spend a lot of money to buy the design tools needed to use this card? Not even $1. Efinix provides all bitstream design tools (integrated into EFINITY) under a free license. Furthermore, it also provides you with an Eclipse IDE suitable to design the firmware that you may need if you also integrate a 32 bit Soc RISC-V Sapphire into the FPGA.