“open source software” what dose that mean?

Open-source software (OSS) is computer software that is available in source code form for which the source code and certain other rights normally reserved for copyright holders are provided under a software license that permits users to study, change, and improve the software. Open source licenses often meet the requirements of the Open Source Definition. Some open source software is available within the public domain. Open source software is very often developed in a public, collaborative manner.

NO open source software means you can use it, develop it, distribute it, it totally free to do what you want with it
read this >> http://en.wikipedia.org/wiki/Open-source_software

Open Source software is not a spying type of software. Some times it is a program ported to another operating system. Firefox is open source ported to Windows, it was originally a Linux Web Browser.

Open source is normally free, maintained , fixed and repaired by developers of the Open Source Community. The source code is under the GPL license which keeps it free, where you can alter, modify and change the source code to meet you needs and requirements, but you also agree to have that code available for other people to use and change.