Yet another license question

[eluser]Unknown[/eluser]
Hi!
I’ve read a lot of topics discussing the CI license and I have to admit that I don’t understand it in full despite Derek’s and other people’s efforts explaining it (more than once).

My question is: Can I use CI for the development of proprietary applications or are applications built using the CI framework automatically open source? I think of GPL in comparison to Lesser GPL or MIT.

I have been using CakePHP for a while but am not quite happy with it and would now like to switch to CI. I understand that the CI license is permissive but how permissive is it? The license issue is important to me.

Can someone please explain this to me? Thanks in advance.