WordPress MU

Welcome.
I know, WordPress MU is on "GNU GENERAL PUBLIC LICENSE" and I have a question about this: e. g. when I modify default theme, files wp-admin and other I must leave information on the modifications or any else?

What about TERMS AND CONDITIONS, point 5: http://www.gnu.org/licenses/gpl.html

Nope.

If it's for your own project, you do not have to release it.

If it's for a client, they have the right to do whatever they want with it, including release it.

So if I have to distribute I must leave information on the modifications?
If you share create a blogs for users I don't must?

Not sure what you mean by "leave information on the modifications". IANAL (i am not a lawyer), but you can remove, edit, modify anything and everything you want, that includes removing any mentions of wordpress mu from it. The license comes into play mainly if you want to redistribute parts or all of the license holders code.

Others also think so?

In all honesty, if you're concerned about the issue, I'd be talking to an attorney who specializes in Internet or Copyright law.

The GPL has been batted around a great deal recent within WordPress circles and it seems like everyone has their own opinion and what they feel is correct. It's also been a very sore issue for some. I feel like that's why you may not be getting responses on this. (You may note that you;re not hearing my opinion on the matter and this is with an Internet law firm on speed dial and paying $2k a month retainer. :)