The use of open-source code in mobile app development is exploding. Flexibility, increased innovation and shorter development times are just three reasons developers are turning more frequently to open source.

According to the sixth annual Future of Open Source Survey, recently conducted by North Bridge Venture Partners and Black Duck Software in conjunction with The 451 Group, open-source software (OSS) investment increased by 49% to US$675 million in 2011. The quality of open source—and the ability to continuously improve it—are two of the top reasons for its adoption, the survey said.

With more than 10,000 new mobile open-source projects launched in 2011 (bringing the cumulative total to over 18,000, according to Black Duck’s KnowledgeBase), the use of open-source software in mobile app development shows no signs of slowing down.

“Open source is the foundation for mission-critical apps in the enterprise,” said Rod Cope, founder and CTO of OpenLogic, a provider of enterprise open-source software scanning and governance solutions. “Nearly all mobile developers are now using open source.”

“There’s so much good code available in the public domain,” added Mahshad Koohgoli, CEO of Protecode, a provider of open-source license-management solutions. “Good developers don’t write code from scratch anymore; they know how to find that code.”

This trend of using open-source code in mobile app development is bringing to light new legal responsibilities and design considerations for app developers. As a developer, you should know the following best practices for successfully using open-source code in mobile apps.

One best practice is to choose a basic development approach at design time. “The first step is to evaluate the size and depth of your project,” said Dave Gruber, director of developer relations at Black Duck, a provider of solutions for automating the management, governance and secure use of open-source software. “Decide early on just how much code you will do natively and how many open-source components you plan to use in your mobile app.”

Another best practice is to learn your company’s open-source license policy before you begin development. “Your company should have an open-source license policy set in place,” said Gruber. “Make sure you understand the policy so as to avoid a negative code audit at build time. Know if you will be using the Apache license, the Mozilla license or other licenses.”