In general, you should use one of the MIT, Apache, or BSD licenses.
If you choose a variant of GPL, it heavily decreases the likelihood of others, especially companies, using your code.
If writing closed-source software, only use other software which are MIT, Apache, or BSD licensed.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
You cannot link your proprietary program to any GPL v3 program.
Linus does not like GPLv3 due to blocking Tivolization, restricting hardware from running modified versions of GPL software.
See Tivoization
LGPL
Same as GPL but you can dynamically link to it from proprietary software.
However, you must provide source for the version of the library you are using.
