I have a client and they have developed a new proprietary software app using open source GPL software.
They were distributing app w/o giving out source code. This is not allowed under GPL. You can modify GPL'd software and include it within a proprietary software app but can not distribute it. Google/Yahoo and many other service providers do use modified GPL'd software. But they simply don't distribute it to 3rd party.
I am glad that they are now distributing source code. If you are in such problem I recommend following resources:
- Official GPL License - A must read for you.
- Wikipedia GPL page - You will get tons of information here.
- Understanding Open Source and Free Software Licensing by Andrew M. St. Laurent - This is an excellent book explains your licensing options, how they compare and interoperate, and how license choices affect project possibilities. If you're an open source/free software developer, this book is an absolute necessity.
- Open Source Licensing: Software Freedom and Intellectual Property Law - A complete guide to the law of open source for developers, managers, and lawyers
- Producing Open Source Software: How to Run a Successful Free Software Project
And simple answer to this question is NO :)
If you have more resources or suggestion please feel free to leave a comment.