OpenGBH (or OpenGTA2 in other words) is a game implementation created on the wave of OpenGTA (GTA1 implementation).

Need original GTA2 files.

The author wrote the instruction:
The first step was to download GTA2INSTALLER.ZIP from the Rockstar Classics page and extract it to /gta2/
Further list of actions:
* Run ./gta2/unpack-gta2installer.sh. This program should recognize GTA2INSTALLER.ZIP and decompress it.
* Run ./gta2/GTA2.exe with wine
* Install GTA2 in your directory
* Change directory from ./gta2 to your GTA 2 installation directory. This should be done in order to copy all necessary files from GTA 2 installation folder to GTA 2 directory.
After that you can delete your original GTA 2.
* Run ./0-compile.sh and hope you have all required libraries of different versions installed (if not, go to ./0-compile.sh and open
./include/ read_this.txt for error details)
* Run ./1-generate.sh. This program will convert GTA2 files to OpenGBH format

The project site has gone into oblivion, including svn. OpenGTA2 seems to have been abandoned for a long time, but at the time of 2014 the author said that the project was not abandoned, and that the author was busy with other things.