Well, gents, I'll try to answer your questions (I'm Stuart Marshall, credited with the grand-sounding title of Editor in Chief of OSRIC... actually it seems to mean Chief Cook and Bottle Washer!)
Before I begin, though, I need to say that as one of the principal authors of the document, I'm constrained by the OGL. That means that I can't indicate compatibility with any particular product without permission... So I can't say, for example, what Morrus said earlier in the thread.
As correctly noted above, OSRIC is still very much under construction. The
rules are in their final form, but there are some proofreading issues in the document (I haven't been consistent with my use of the serial comma, I suspect there are both British and American spellings, etc.) and so on.
You could use OSRIC for its intended purpose as it is now, and I've no plans to change anything major, but what I don't have yet is a commercial-standard perfect version.
The OSRIC document itself is free in .pdf format, and OSRIC is a non-profit exercise. It's a 132-page rulebook of ~90,000 words. The final version will also be free in .pdf format.
I was surprised to learn that there seems to be a demand for printed books as well. I've decided to produce these (at cost, since it's a non-profit) but obviously not until I have a final version; the current plan is to distribute it via Lulu, and if you're interested, you'll be able to buy the book (perfect bound) for something in the region of $7.50 plus shipping.
The
purpose of OSRIC is twofold.
First and foremost, it's a vehicle for publishers. Expeditious Retreat have led the way here, and as noted, their adventure Pod Caverns of the Sinister Shroom is available in .pdf format now. It will be available in print in September.
The idea there is that the publishers will be able to say that their document is "compatible with OSRIC." (Anyone can do this, without asking permission from me, and there's no need for a fee or royalty to me of any kind.) I hope that the buying public will understand that this means your publication is compatible with other systems as well, if you follow that... I realise this is vague but I'm under the constraints I indicated earlier.
Secondly, it's an openly-usable label for your publication. In other words, if you say you're selling something compatible with OSRIC, you'll benefit from the marketing that other people have put into their own OSRIC-compatible stuff, while they will also benefit from your own efforts.
I should say that I don't expect anyone actually to
play OSRIC.

I just hope that there will be sales of OSRIC-compatible materials, which will end up being used with other game systems, including - ahem - the game so many of us grew up playing.
I know I've been a bit vague; I'm working within constraints suggested by legally qualified people.
I'd be delighted to answer any other questions anyone has, and indeed I'd be grateful for the opportunity to do so.