develop an exporter extension for SketchUp using the Ruby API or the C SDK to export to the file format of your software,
or use the C SDK to write an importer for your software that can read .skp files.
For the Ruby API, there is no specific exporter class. You basically create a file for writing to (File.open('my_file.xyz', 'w'){ |f| f.puts('text') }) and traverse the active model. Be aware that SketchUp models have a nested component hierarchy, so to export the entities contained in a component you can call the same code that you used for exporting the entities of the top-level model. Even better is to traverse the definitions list (to avoid exporting a component multiple times) and the instances they refer to.
For creating an exporter using the C SDK, you go to “Data Structures” and then “SketchUpModelExporterInterface”.