Ok, so i have to develop a DHCP server for my school, but it has apply to some rules.
I know you can download for every popular distro an easy DHCP-server and install it en get it working, no problem there.

The problem here is:

it has to filter computers by mac address

it has to work in different VLANS and by different VLANS i mean that i has to get an IP-ADDRRS that is assinged to that VLAN.

It has to have a GUI interface for adding/ blocking/ deleting mac addresses.

who can help me out here. Money isn't a problem

Just a quick tip regarding the mult-VLANS environment:

To have the DHCP server distribute addresses belonging to the right VLANs is not a problem.
On the default router of each VLAN you need to redirect DHCP broadcast into a unicast towards the DHCP server (as broadcasts stay inside the VLAN, they would never reach the DHCP server if it is in another one).
Once you do this, the DHCP server will recieve a DHCP request coming for the IP@ of the PC's default gateway. So that the server will know in which VLAN is the requester is and will offer the 1st IP@ available for this VLAN. Get it?
Now to redirect DHCP broadcast into a unicast it depends on the router you're using. If it's a cisco, then the command is:
(assuming 192.168.1.1 is the IP of the DHCP server)
You need to type this command on each VLAN's interface of the router (well, only if you have some potential DHCP client in the VLAN of course).

Hope this help
Good luck for the rest!