Not only are there very few DO gas programs, the info provided via the "AOA Opportunities" web page is rather wanting, esp when compared to FREIDA (the AMA analog). Unless this has changed since I was an applicant, I doubt that it has, your best option is the old fashioned telephone for the DO programs...and still not a bad option to approach the MD programs either.
Furthermore, GasMan2003 makes a valid assertion, in my opinion, regarding the quality of the AOA gas programs. And, just as he claims, I found them ACGME programs...all of them that I applied to...to be very DO friendly.