I've migrated the demos of most of my books, from a hosted SVN repository (at code.marcocantu.com/) to GitHub, in a new organization called MarcoDelphibooks, at github.com/MarcoDelphiBooks. In my code site, I had a single repository for older books, and one for the Object Pascal Handbook. On GitHub I decided to create separate repositories, making it easier to grab only what you need and even download a single ZIP for the entire project.

In the migration process, I cleaned up only the Object Pascal Handbook repository, recompiling all demos with Delphi 10 Seattle, and I plan to keep them up to date with the latest release of Delphi going forward. Other books are version specific, so it makes more sense to keep the original demos as they were and as they compiled in the version they were created for. I might create separate repos for collection of demos for different product areas (VCL, RTL, Database) updated for the latest Delphi, but that's a separate project.

Hope this helps making them more reachable and easier to interact with. In the short term, I plan moving also my other demos repositories (still at code.marcocantu.com) to 10 Seattle and to GitHub, and look also for demos of older books and publish them as well. I plan closing my personal, paid, subversion hosting site ASAP.

I'm still far from a Git and GitHub expert, and welcome any feedback, interaction, suggestion.