Original sentence: Fees from sale and licensing of commercial software are the primary source of income for such companies.Moreover, many see the introduction of free software as damaging to the market for commercial software.Most software development companies sell licenses to use individual copies of software as their primary source of income, using a combination of copyright, patent, trademark and trade secret laws (collectively called intellectual property rights laws).The most obvious complaint against open-source software revolves around the fact that making money through some traditional methods, such as the sale of the use of individual copies and patent royalty payments, is much more difficult and sometimes impractical with open-source software
Edited sentence: Although most software is written for internal use, fees from sale and licensing of commercial software are the primary source of income for companies which sell software.By keeping source code hidden, they usually make it impractical to make changes to a program they develop, and demand fees for its use and improvement.Some software development companies sell licenses to use individual copies of software as their primary source of income, using a combination of copyright, patent, trademark and trade secret laws (collectively called intellectual property rights laws).The most obvious complaint against open-source software involves the complaint that making money through some traditional methods, such as the sale of the use of individual copies and patent royalty payments, is much more difficult and sometimes impractical with open-source software