Why do people give away the source code to their software for free?
There are a variety of reasons people do this but I find the main reason is people believe in the community (everyone) should have access to the software. It's also to let the community validate that they are not doing anything nefarious with anyones data. (Unlike companies like google and microsoft).
Other times a company may have a massively complex software that not many people can admin on their own and they will charge a fee to load the system, bug fixes, etc.
If I run open source software, do I have to make that code available to the public?
Generally speaking the answer to this question is yes and no. LOL, that's why it's imperative that you read the open source license that comes with it.
For example, some licenses may mandate you make the code publicly available ONLY if you modify the original source code, so if you take any of my software for example, if you change something, you have to give that change to the community. That is the whole ideology behind the Open Source Software movement.
Can I start a software company on someone else's code?
The answer to this question is yes, no and you can, but really don't want too. That's why it's imperative that you read the open source license that comes with it and if you don't understand the language, consult an attorney.
Some licenses restrict use for commercial applications and some don't. The suite of software I currently offer does not have restrictions from someone starting their own Trello or google docs type of a service. Again, if you do, keep in mind you will need to make the code available to all if you make any changes to the core.
The projects listed below are the projects I'm currently working on. Lawless Archives, Wiki and Links will be coming available soon however I'm in the process of testing them still. All projects listed below have the source code fully available for download and all are able to be used in commercial purposes. Make sure to read the license that comes with the software as there are some requirements you will need to be aware of. Everything you need to know about the respective systems is listed in the Lawless Wiki, so if you have any questions that is the best place to start.