You don't "have to" supply a license just to post code and have other amateurs use it. If you're not using ridiculous GPL shit, you don't have to do anything other than mark out which parts of your code are stolen from others and include a copy of their terms.
The problem is, a professional still can't use code without knowing where it came from and being able to show that he has a right to use it; a license. If you want to not be a dick about your published code, you should give him one. Nothing has changed.
Name:
Anonymous2011-01-25 19:49
both license types have unacceptable obnoxious clauses (such as reproducing a huge disclaimer that is written in all caps) that severely restrain our freedoms
Seriously, wtf.
/*
* <one line to give the program's name and a brief idea of what it does.>
* Copyright (C) <year> <name of author>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>;.
*/