Submitting other people's work to the arXiv This is a soft question aimed at establishing what people think is the professional best-practise for submitting unoriginal work on the arXiv.

There is a draft of an article [1] by Robert Szelepcsényi, at his webspace at the University of Chicago, apparently written more than a decade ago during his graduate studies. The work seems to be  correct, modulo some very minor errors, and contains a result that I would like to refer to, independently of what the University of Chicago intends to do with that webspace. It seems to be available only at that single location; and there doesn't seem to be any publicly available works which duplicate his results.

Partly for the sake of ensuring its correctness, I have taken it upon myself to write notes recapitulating the results and motivations of that draft, acknowledging that it is essentially a recapitulation of [1], and which hopefully smooths over some of the roughness present in the existing draft. I can certainly put these notes online on webspace of my own, but at present the arXiv seems to be the most responsible place to submit this draft for future reference.

Question.

Assuming correct attribution, and granted that these results are not widely available otherwise, is there any particular reason that I should not submit my draft of Szelepcsényi's results on the arXiv?

[1] Logspace MOD Classes with Composite Moduli (Preliminary Version) &mdash; Postscript File
This should be perfectly acceptable if it is framed as an exposition article. There is a long tradition of expository articles in mathematics (one example that comes to mind is Thurston's exposition of a method developed by Conway to determine if the plane can be tiled by a given shape, see here). Just make sure that the abstract and the introduction convey that all you're doing is to explain Szelepcsényi's proof.