This grew to large for comments so I just decided to post it whole here:
Ok, as for market share the latest numbers I've seen put the market at 47% play current edition D&D and 53% play 'other'. That 'other' gets broken down to about 3-5% playing 'classic' D&D (OD&D-AD&D2e) with the other 50% being players who play some variant of 3x.
Since most OSR is based on the SRD that places them in the 3x crowd. Unless you are playing only an original TSR product then you get lumped in with everybody from Paizo on down. So I think the total old school is a larger number than what is just represented by the 3-5% spread.
I have addressed some folks about this subject as I run across them and just thought it would be good to do a post on it.
As for what requires a license, unless you are creating something completely independent of all current OSR games (S&W, LL, C&C,etc) you HAVE to post the license. I see some doing this with blog content by declaring that the text that follows is OGC and hot linking it to a page on their blog that is the OGL. That is very good for the blogosphere.
I'm not going to name names or point fingers. I understand some may not be clear on the OGL requirements but ignorance, as a judge would say, is no excuse for violating the license. If you are going to put up in public either a document or a post you HAVE to do it. Also, I don't want to make a roadmap for others to follow to compile violations.
Here is the license in rtf format:
Notice that the license isn't predicated on whether or not you are Paizo making and selling a product or just a hobbyist posting variations of a SRD monster for free. You have to follow the license regardless.
I am a (soon to be) publisher and really don't want the rug snatched out from underneath a year and a half of time and money spent on development because WotC compiles enough evidence of violations to revoke the license.
And it's not my point...it's a legally binding license by a company who wants to see us gone. Let's not give them the bullets to shoot us with.
For the good of the community I'm just asking that everybody keep these things in mind.