As above but with git submodule or SVN externals.

同上，但使用git子模块或外部svn。

Every submodule of a free module is a free module.

自由模的任何子模还是自由模。

Acme's membership database is a core piece of its membership submodule.

Acme的成员数据库就是其成员子模块的核心组成部分。

I do think it's pretty uncommon to use a submodule for production-ready code.

我想使用一个模块的生产就绪的代码很少见。

Wireless signal acquisition system is composed of host module and several submodule.

无线信号采集系统由主模块和多个从模块构成。