Here are the required steps for compiling 0.9.3 on Ubuntu 8.04 Hardy:

First install the required dependencies (if you do not already have them)

sudo apt-get build-dep mscore

Download the .tar.bz source from Sourceforge, uncompress, compile and install :

bunzip2 mscore-0.9.3.tar.bz2
tar xf mscore-0.9.3.tar
cd mscore-0.9.3

make

[go drink a coffee until it's finished]

cd build
make lupdate
make lrelease
sudo make install

Hint:
the revision of cmake coming with ubuntu (currently 2.4) may be not sufficient. To build mscore cmake rev. 2.6 is required.
Set the following two variables in mscore/CMakeLists.txt to false;

set(BUILD_SCRIPT_INTERFACE false) # this requires qt >= 4.4 && cmake 2.6
set(BUILD_SCRIPT_DEBUG false)


To set

set(QT45 false) # set to true if you use qt >= 4.5.0

may be also helpful.