After downloading the source code I right clicked it then "Convert to maven project", isn't it supposed to fix all the errors? It still has more than 10,000 errors.
EDIT: I fixed this by unzipping eclipse with something other than winrar. Winrar didn't unzip files with really long names
All you have to do is carefully read the following book
http://www.sonatype.com/Support/Books/Developing-with-Eclipse-Maven