Licensing Issues

Hello There,

My company wants to make a commercial SIP PBX based on the asterisk open source software. We want to modify the source and build a embedded device. I would like users to share their opinion on the following questions:

  1. Is it legally OK, if all the modified sources are made available on our ftp site to commercially sell the hardware with the asterisk software ?

  2. Or is it necessary to get either a OEM or a commercial license from Digium ?

If any of you have experience in licensing the asterisk software from Digium, what advantage one gets because of this that cannot be achieved through open source.

I really appreciate any of your inputs.

Prasad Kandikonda.