1.get the source code from the offical web site. here
2.It needs ogg_static.lib, vorbis_static.lib and theora_static.lib ,etc to build the project. if you don't have these libs, and if you use source code 2.4.1,you can get these libs from here
Note:
you can also communicate with the develop team with IRC to get the dependance libs. ( Another way to get these libs: Stratagus is the RTS engine which used in BosWar. The external libs mentioned above can be abtain in Stratagus source code. You can read the install steps in Stratagus_SRC_ROOT/doc/install.html, it will tell you how to get the libs.)
3.build it.
it works well.
Good Luck!
How to communicate with Boswar team through IRC:
1. download IRC , i will take mIRC as an example, and install it.
2.lanuch mIRC. It will prompt you to nput a IRC server. You can use irc.freenode.net then it will prompt you to input your email and id to logon,
3.press the 'Favourites' icon on the tool bar, input 'bos' as a channal name ,then press 'join'.
That's all!