There's always an up to date build in the bin/ directory of the distribution.
In order to (re)build boo you are going to need to have the following tools already installed:
git clone http://github.com/bamboo/boo.git boo
Boo uses the nant buildfile default.build to provide the following nant targets which can be used to build, rebuild, test, install and clean the boo project. This is done to make it as easy as possible for users to perform these automated tasks. All you have to do is go into your newly downloaded boo directory and start invoking nant with different targets, its easy:
on mono the unit tests must be executed directly from the command line:
nant compile-tests && nunit-console tests/build/*Tests.dll