I'm not really sure on the summoned shadows bit. They are 100% positively not undead, but their level of intelligence I'm not sure of. I think if you spoke in Shadow it would understand and could even speak back if it chose probably, but only two Shadowdancers are able to communicate in that fashion.
I've seen them played with a basic understanding of the SD summoner even though they don't speak, and that seems to make sense, otherwise you have to wonder what they're even defending you for, right? Well...ideally. Sometimes. Usually it's more like...
Shadowdancer's Companion: "I'm a Lover, Not a Fighter" Shadow Fiend
The nimble dancer between light and shadows ducked another blow and stepped back with a grin, cloaking herself in the shadow cast by the very creature attacking her to circle around...then her eyes widened in uncertainty as the monster swung again, its eyes glinting with the light of the Weave. Its gazed pierced the darkness that hid her with the Sight; she had to make a quick retreat. Thinking quickly, she reached out again to the dappled patches of shadow to call one to her side to serve as a distraction as she made a hasty exit. "Aid me, I beg you!" she cried.
The light filtered out around a wavering form as the shadow appeared, and without looking back she made a break for it, hoping its ineffectual blows would take the attention from her... Then she felt the raking pain of claws slashing across her backside and she fell onto the floor in shock. Turning her head as she looked at her end, she saw behind the looming form a shadow standing still, making no effort to stand in its way... its uncanny eyes met hers and then it solemnly faded away as the blow came down... She had just enough time to call out, "Curse you, Shadow Friends...!" before she saw no more.
As far as Shadow Walk goes, anyone with some casting ability can make illusions anyway...it's a whole school of magic. Necromancers are certainly not the only people that can create undead. They're just the specialists. I've been behind giving love to wizard specialists as the elite in their schools of magic for ages, but I'm not sure what a question on SD illusions had to do with what is basically an illusionary teleport. SDs are also 'supposed' to have Shadow Jump, which they don't here and is a far better equivalent ...comparing it to a silent image is like "she can make shadows wave around so I should be able to teleport with it!" heh. At least compare lower-level abilities.
PS: I realize the bulk of this post was making fun of observation-only shadows, but it's one of those days! :P