Many authors put up their lecture notes online on their personal webpages, available for anyone to download, but many of them don't include a license. Are you allowed to download them or not (as someone not in their university/course, but they put it up on their webpage so anyone can download it)?
As an example, you can look for lecture notes on any topic, most of them won't have a license at the beginning.
(Specifically, I'm asking about Germany)
That doesn’t mean you can’t download it, it just means that you have to comply with whatever fair use/fair dealing rules are for your jurisdiction. Downloading in some circumstances will be fine, in others it won’t exact details vary by jurisdiction. See What is the practical difference between "fair use" and "fair dealing" in Copyright law?
German copyright law does not recognise a general ‘fair use’ doctrine. Rather the Copyright Act contains a chapter including several specific provisions limiting the scope of rights for the copyright owner with respect to lawfully permitted uses. For instance, such lawfully permitted uses refer to collections for religious use, newspaper articles and broadcast commentaries and, most importantly, the reproduction for private and other personal uses.
