Git, the open source distributed version control system created by Linus ... But a key portion is not; while the code for fetching files and interacting with a remote Git repository is all open ...

Some are commercial, such as IBM Rational's Clearcase or Microsoft's Visual SourceSafe; others are open ... control for any source code (whether it be C, C++, Java, VHDL, Verilog, and so forth) should ...