Install the provided binaries or see this instruction.
See special instructions for iOS.
If you don't need or want the latest developments (available via GIT), just use the packages provided by your distributor. If they don't exist, check the next section and/or ask the distributor to make a package.
The use of the most recent release is strongly suggested!
Make sure you have SDL, python, zlib and a compiler installed (with all their header/devel packages if they exist). You will also need either cmake (recommended) or autotools (unmaintained).
When not using an IDE to build, make will be required. Also, on Windows a Cygwin environment can be used instead of MSVC.
First you'll need to get the source. Either in the form of a release tarball or the latest source from GIT (preferred).
The advantage of the development tree is that you always have the most updated version, with bugfixes and features added after release. Of course, you may also get extra bugs, while the changes are being polished.
This probably gets more complicated if you're on Windows because, but you can try running the builds from here.
Download the source tarball from the project page.
Create a (readonly) checkout of gemrb in the current dir with:
git clone git://github.com/gemrb/gemrb.git
If you have the tarball, extract it. The rest of the instructions are the same as for building from Git. First move to the source directory then run the following:
mkdir build cd build cmake .. make -j2
By default, GemRB is installed into /usr/local (“fhs”). You can pass -DLAYOUT with “home” or “opt” to change the general layout and -DPREFIX to change the install path prefix. Pass -DCMAKE_BUILD_TYPE=Debug to cmake if you want to create a debug build.
If you're using one of the available project files, just build as usual.
For a self-compiled gemrb, installation is not necessary and you just need to use a different configuration file. See The minimal dataset for a good starting point.
Otherwise run the customary: make install
After you have the games, you can also install mods. Most WeiDU mods will work out of the box, but some may have problems due to case sensitivity. Report such problems to the mod's authors.
If you already have a game installed somewhere, even if it is on another OS, just make sure that that filesystem is mounted (writable or you won't be able to save!) and point gemrb to the relevant directory (set GamePath in the configuration file).
Just run the normal Setup.exe and follow through to the end. You can complicate the matter by using packed ISO images as described here. Remember to do a full install.
There is a free bg2 demo available. You can get it from FilePlanet or elsewhere on the net.
Install it like it was a game from the previous sections.
You can also try NJW's GemRB Installer.
Setting the paths can be tricky, so carefully read the errors that gemrb prints to the output before exiting. See this video (linux) for a walktrough on how to fix the encountered problems and set up the paths properly.
Use the external launcher.
You will know gemrb is working perfectly once you can see the main game screen. If that doesn't happen, check the console for errors and fix the configuration file as needed. Usually some path is set wrong.
Since 0.6.1 GemRB comes with a minimal dataset, that can be used to check if gemrb is configured correctly right out of the box.
If you installed gemrb, try the included fhs.cfg:
gemrb -c /usr/share/gemrb/minimal/fhs.cfg
If you don't want to install, you can just run the sample config from the build directory as-is:
gemrb/gemrb -c ../gemrb/GemRB.cfg.noinstall.sample
It will exit as soon as it loads the Start script. That is the expected behaviour.