Skim is written in Objective-C with the Cocoa libraries. In particular, it makes use of the PDFKit framework to do much of the PDF rendering.
In order to contribute to the main programming, a basic knowledge of Cocoa programming and Objective-C is necessary.
There are currently few formal procedures for code review or coding standards. Most suggestions for improvement are expected to be discussed on the developer list before committing.
All The source code necessary to build Skim is available in Subversion. There is a separate page on how to use the Skim Subversion Repository.
Once you have downloaded the source, you can build Skim using Xcode. Xcode 8 or higher is required.
If you want to help localize Skim in your language, please tell us on the users list. There is a separate page to explain what needs to be done to add a Skim Localization.
Wiki: Main_Page
Wiki: Skim_Localization
Wiki: Skim_Subversion_Repository