The UN comes with the UN Open Source Principles, these provide guidelines to drive collaboration and Open Source adoption within the UN and globally. Supported by the OSI.
https://unite.un.org/news/osi-first-endorse-united-nations-open-source-principles
You can support is too! By filling out a Microsoft form...
Don't blame them for picking a proprietary form service, it is not doable for a small organization to setup or rent something like a Limesurvey, Cryptpad of Framasoft server. They don't have the knowledge nor the budget.