For all OPUS FAU dissertation publications available in digital-only format there is an indexing & abstracting contract with ProQuest (PQDT). FAU doctoral students are eligible for a royalty from these based on sales and use of their dissertation, provided they contact email@example.com and set up an account. Royalty rates are currently set at 10% of net income. See here (https://opus4.kobv.de/opus4-fau/home/index/help#rulesfordiss), Section „ProQuest Dissertations and Theses (PQDT)“.
In addition authors can register documents they publish in FAU OPUS for dividends with the registry portal T.O.M from VG WORT https://tom.vgwort.de/portal/index. See here (https://opus4.kobv.de/opus4-fau/home/index/help#vgwort).