1) Whilst it can be used to make a profit, it can also be used as a system to allow you to trade storage space on your own computer in return for replicating your own content on other people's machines. The more storage you provide, the more redundantly your own content is hosted on the network, and the longer you can still serve your own content whilst your own machine is offline. IANAL though, so I can't comment on the legal implications.

2) Sure, you can view it as a CDN anyone can participate in (including machines within your LAN).

3) There are plans for handling DMCA takedowns https://github.com/ipfs/gateway-dmca-denylist