Which of the following is the PRIMARY risk with using open source software in a commercial software construction?

While open source documentation quality varies, lack of documentation is a development inconvenience rather than a primary legal or business risk unique to commercial use.

Many open source licenses, especially 'copyleft' licenses like the GNU General Public License (GPL), require that any software incorporating or modifying the open source code must also be released under the same open source license, forcing companies to disclose their proprietary source code. This 'viral' nature of copyleft licenses poses a significant legal and competitive risk to commercial software vendors who wish to protect their intellectual property. Failure to comply can result in loss of license rights, litigation, and mandatory public disclosure of trade-secret code.

Most open source licenses are perpetual and do not expire, making license expiration a non-issue and an inaccurate characterization of how open source licensing works.

Support costs are a consideration for any software, and many open source projects have commercial support options available; this is not the primary or distinctive risk of using open source in commercial products.