Ask HN: Open source hotel booking software

I am looking for, preferably C#, hotel booking software. Ideally it should be able to handle lots of hotels, only booking, no payments but most of all I am just looking for a good starting point. Someone must have had this issue before, it cannot be necessary to build from scratch.

As the description probably reveals I am looking for open source, free or with the possibility to buy the source code.

Other types of booking software might be altered into handling hotels, so if anything comes to mind, please let me know.