There are many different types of licenses that open source projects use, so in this post I will cover the most common ones with the distinction of which ones you should be wary of using if you are interested in developing proprietary software using the open source project.

Licenses that you can not safely use for proprietary software:

• GNU GPL
• GNU LGPL
• Some ambiguity of when you have to share your proprietary code. The wikipedia article discusses the distinction of statically vs dynamically linking the open source code: http://en.wikipedia.org/wiki/GNU_Lesser_General_Public_License

Permissive licenses that you can safely use for proprietary software:

• MIT license - Very short license with few restrictions http://en.wikipedia.org/wiki/MIT_License
• Apache - http://en.wikipedia.org/wiki/Apache_License
• BSD - https://www.freebsd.org/doc/en_US.ISO8859-1/articles/bsdl-gpl/article.html
• ISC (Internet Software Consortium) - http://en.wikipedia.org/wiki/ISC_license; Functionally the same as MIT / BSD

Hybrid:

• Mozilla Public License - The one major exception I found to the two categories is the Mozilla Public License which requires you to open source code files that are under the MPL, however your proprietary code doesn't need to be open-sourced. It's an interesting compromise between GPL and the permissive licenses listed above, however I fear that it may actually be a logistical headache to comply with.