There is now a system reference document (SRD) available for Openquest 3rd edition. The SRD is free to download from this link, and will eventually be hosted as a HTML document on the d101 Games website here.
I haven't had time to write an in-depth review of Openquest 3rd edition, but the changes are substantive and wide-ranging from the first two editions, and overall they are positive cointributions to the system. Openquest's 3rd edition keeps its place as one of my two favourite implementations of the Basic Roleplaying system (BRP) alongside Mythras.
Mythras appeals to the lover of crunch in me, but Openquest is an excellent, rules-light version of BRP that keeps many of the details that appeal to fans of BRP while simplifying and economising many of the rules that newcomers find fiddly. I think it's one of the best introductions to BRP that one can get. If you want a system that does not have levels, classes, or inflating HP, that makes combat feel deadly and exciting, and that sharply distinguishes between how different kinds of magic work, you might find the BRP family, and in particular Openquest, a product that appeals to you.
Along with the SRD, there is a free quickstart scenario and rulebook that contains most of the rules (it leaves out some of the magic systems available in the main rulebook).