What are the details of the license it appears under?
Why was the community not consulted nor even informed regarding the move away from open source code?
Was the reason for the switch to proprietary code really security through obscurity as explained by Ken Francis: 'Code must now be protected in order to keep the website and membership information safe.' [ https://www.warmshowers.org/comment/24683#comment-24683 ] ?
Are there people involved with Warmshowers who are familiar with the code and able to debug problems or add new features? If not how will necessary corrections/additions be handled in the future?