pretalx is open-source conference management software. It covers the whole chain of an event: the call for papers, the submission and review of proposals, communication with speakers, and building and publishing the schedule. Organisers of conferences, meetings and meetups use it to select proposals and manage the programme. You can install pretalx yourself (according to the documentation it runs on Python with PostgreSQL and Redis) or use it as a hosted service at pretalx.com.
pretalx is maintained by rixx.de software development, a business in Germany that also operates pretalx.com. The source code is under the Apache licence. According to its privacy statement, pretalx.com runs on servers in Germany and the service is subject to German data protection law. If you install pretalx yourself, all data from speakers and submitters stays on your own infrastructure. On the hosted service, the event organiser has access to the submitted data.