In general, yes. And even if it's not, people (read: academics) almost universally don't really care and will send you their paper anyways. The main thing is so

In general, yes. And even if it's not, people (read: academics) almost universally don't really care and will send you their paper anyways. The main thing is sometimes getting more well-known professors to reply which is a whole other topic, but most will still be happy to share their paper. Re: your latter case, yes. I suspect that automating this process will likely lead to worse consequences (sharing papers via email is something that everyone-knows-that-everyone-does kinda thing, even if it may not be "fully legal"—whatever that means), but setting up infrastructure to share your papers (even with approval) is likely to be met with some amount of resistance and probably not-greatly-worded letters from publishers. To be fair, a good chunk of useful publishers (not all... I'm looking at you, Cell) are moving to allow reviewed articles on authors' websites, but almost all journals allow preprints to be available on open sites (and be submitted for review).