Apaleo is a Property Management System which is purported as an Open PMS. It provides API access to all its users and vendor partners as well as an App rich marketplace where customers can choose from over 200 Apps to improve their PMS.
MongoDB is an open source cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with optional schemas. MongoDB is developed by MongoDB Inc. and licensed under the Server Side Public License (SSPL) which is deemed non-free by several distributions.