There are some instruction how to checkout and build netbeans platform:
Unfortunately it does not work due to missing module (editor/mimelookup).
This document is obsolete for trunk builds. (Please note that it does not claim
to apply to even 5.0, much less 6.0.) You need to use the 'checkout' target, as
documented e.g. here:
Checking out a fixed list of directories is inherently unreliable.
We recently moved out from Collabnet's infrastructure