I don't commercially exploit most of my work, so I prefer to release it under an open source license. Even though I sympathise with the activism behind the GPL license, I dislike it's lock-in properties.
Hence I prefer an open source license, such as Apache v2 license, BSD license, MIT license or ISC license. The later three are very short, almost equivalent licenses. Apache is significantly longer, and also deals with granting patent rights. Since I don't have any patents on my name (and if so, I would prefer to license it separately), I prefer one of the shorter licenses.
I prefer the ISC license, because it is very short; it removed all the text that was made redundant by the Berne convention. Whilst it is the least popular, it is the most recent, and shortest.
Copyright © Year, Copyright holder
Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.
The software is provided "AS IS" and the author DISCLAIMS ALL WARRANTIES with regard to this software including all implied warranties of merchantability and fitness. In no event shall the author be liable for any special, direct, indirect, or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of this software.