Streaming _is_ downloading. It's just downloading _continuously_ as the content is presented. Whether or not you seed is an entirely separate issue and has nothing to do with streaming vs downloading.
No, it is not. Not from a legal perspective, which is all that matters in this context. With seeding you are making things worse for yourself, as you are not merely downloading but also distributing. Seeding is also relevant with regards to downloading, as IPFS automatically starts seeding what you download.
