Very carefully Please see: component criteria.
No. Don't install/activate what you don't need.
Yes, it's all Free / Libre / Open Source (FLOSS). You can use different components which suits you better (legacy data, better features, etc.) Please do share why/how you did this so other can learn and make better choices for their projects.
All Software Components are released under an OSI-approved license. Please see each component page for the specific license.
No. The main use case is to set up a server (virtual or physical) for each project. But several can domains can be supported as aliases, so you could have both exampleorg and example.com but only one user johh.smith
An alternative: Factory
Rest of content is still at https://suite.tiki.org/Tiki+Suite+FAQ