SemiSpace runs on J2SE 6.0 or greater. The other components are optional. If you are not intending to distribute, you will not need Terracotta, etc.
If you want SemiSpace to be distributed, you need to download and install Terracotta.
In order to benefit from the webservices proxy (more about this in the tutorial), you need a sensible endpoint. This is in effect a webapp. Choose this at your own discretion. The recommendation is Jetty, but you should be effortlessly able to use Tomcat, or Geronimo as well.
It is presumed that you use bash as shell, most likely under MacOSX or Linux. Scripts and instructions must be adapted at your discretion if you are running something else.
XStream has some optional dependencies, and the XML support library xpp has been configured to be default, but you can exclude it and include a different support library instead. See http://xstream.codehaus.org/download.html for details, or just include the following in your maven dependencies:
<dependency> <groupId>xpp3</groupId> <artifactId>xpp3_min</artifactId> <version>1.1.4c</version> </dependency>
The persistence and webapp sub projects depend on sun jars, which you may have to download and install yourself.
See Maven's guide to coping with Sun JARs for more information.
The semispace-main project does not have any such dependencies, indeed it is depends only on XStream and slf4j logging.