Here's the page the Xabber guys were referred to:
<a href="https://www.bundesnetzagentur.de/EN/Areas/Telecommunications/Companies/Notification/NotificationRequirement-node.html" rel="nofollow">https://www.bundesnetzagentur.de/EN/Areas/Telecommunications...</a><p>It's in English, but the registration form is in German:
<a href="https://www.bundesnetzagentur.de/SharedDocs/Downloads/DE/Sachgebiete/Telekommunikation/Unternehmen_Institutionen/Anbieterpflichten/Meldepflicht/Meldeformular_pdf.pdf;jsessionid=F0427467E2779E03415AF0AB9CD01C6D?__blob=publicationFile&v=13" rel="nofollow">https://www.bundesnetzagentur.de/SharedDocs/Downloads/DE/Sac...</a><p>Here's a cursory overview (IANAL!): They want the name of your company, and for companies outside Germany, the name of a representative in Germany; and a way to contact you. Page 2 concerns access providers, e.g. ISPs. Page 3 concerns service providers, with provisions for all manner of services from VoIP, Email, messaging, VPNs and more general network solutions, and a field for "other" ("include brochure where applicable"). They close with some explanations, and a threat of fines up to 10000 EUR in case of non-cooperation.<p>Fun stuff.<p>The list of companies that have complied is public: <a href="https://www.bundesnetzagentur.de/SharedDocs/Downloads/DE/Sachgebiete/Telekommunikation/Unternehmen_Institutionen/Anbieterpflichten/Meldepflicht/TKDiensteanbieterPDF.pdf;jsessionid=F0427467E2779E03415AF0AB9CD01C6D?__blob=publicationFile&v=62" rel="nofollow">https://www.bundesnetzagentur.de/SharedDocs/Downloads/DE/Sac...</a><p>It's 149 pages at around 20 entries per page (there's also an Excel version available). Facebook is not listed. Google is, hilariously with the note that there is an ongoing legal dispute on whether they are required to register.