VirtualBox supports VNC for guest machines through the libvncserver. Although the old ebuild for 3.2.x series had this added at some point (take a look at bug #348204), the newer version of ebuild based on 4.x.y series has dropped this support.
I've had a look at the current ebuild and configure script for the VirtualBox 4.0.2, and figured out there are small differences that render the old patch for the configure script unusable. I've created a new patch for it, as well as for ebuild to allow enabling of VNC.
Please find the patches attached to this bug report.
Steps to Reproduce:
Created attachment 262951 [details, diff]
Add the --enable-vnc option to VirtualBox OSE configure script.
Created attachment 262953 [details, diff]
Add the USE flag for enabling the VNC in VirtualBox OSE.
+ 18 Feb 2011; Lars Wendler <firstname.lastname@example.org>
+ +virtualbox-4.0.4.ebuild, +files/virtualbox-4-vnc.patch:
+ Version bump. Removed old. Readded vnc USE flag as requested by Branko Majic
+ in bug #355481.
Fixed in virtualbox-4.0.4. Thanks for the patch.