Programme using MIT license should be MIT license also ?

I've used an open source code in my programme. What about my programme?

[seoul]

Before proceeding, lets assume my software is "software-X" and i've used "open-Y" code in my software. Moreover lets assume first 80% of software-X is totally developed by me and rest 20% is built upon that open-Y software source code.

Now, when i deliver software-X to my client i don't wanna give him the source codes, i wanna deliver him just the executable version. I want to keep 80% works of code as closed source.

Is it possible ? I know i have to mention in my software that i've used open-Y software. If i've modified open-Y software then the modified version is in same license as the original MIT license. But what about my other portion of codes which has no connection with this open-Y software ? Since software-X used open-Y software then does it imply that software-X is an open source software also ? Do i need to publish full source ?

[caribguy]

There is a comparison chart of various types of licenses, including the one from MIT. It's part of a licensing HowTo, put together by Open Source Initiative's president - Eric Raymond: http://www.catb.org/~esr/Licensing-HOWTO.html [catb.org]

Not all open source licences are "copyleft" - and cause your work to be licensed under the same terms.