(There is a discussion of this on my website, at www.bricklin.com/licensingthinking.htm.)

Here are some of the general goals I'm trying to achieve with these licenses:

• Be able to afford to create and update software in a self-funding way.
• Make the software open in many ways, both to allow customization, improvement, and learning.
• Have as wide use of the software as possible.
• Have payment come from those for whom the software provides financial benefit.
• Be simple, logical, and fair.

The basic idea is to start from two existing, successful licensing schemes.

The first is the Apache Software License 1.1. The main Software License borrows heavily from there. The idea is to allow general use and modification along with distribution that carries along the license terms.

The second is the original (in 2003) Movable Type Limited Commercial Use License. The Commercial License Companion here is inspired by it. The idea is that personal and educational use is allowed without payment but commercial use requires payment after a trial period. Some tuning has been added to define commercial use in a way related to the way the U.S. government defines a business and the addition of an exclusion for very small entities for whom the payments might be burdensome.

Added is the idea of "commercial distribution". This is when the software is resold by others, or used as part of a service for which payment is received. The license attempts to make this activity trigger normal commercial use payments on each "sale" or use for pay. The desired affect is to allow others to resell the product for whatever they want, and still receive revenue as if the ultimate user had bought the original. The reseller may have improved the product, and charged more than the original, but that extra is theirs. It also allows others to improve their services through use of the product on behalf of customers without the original author feeling that they have lost a sale.

For more information about the GNU General Public License, see the Free Software Foundation's Licenses page and their Frequently Asked Questions about the GNU GPL page.