St George's is a parish of the OCA (Orthodox Church in America). You can read a brief history at its page
on the OCA website. As you can see from the description of its congregation, it's a very diverse group of faithful. Although the OCA's origins were Russian and Rusyn, having been formed at a time when the situation in Russia made it virtually impossible to maintain communion with the Russian Patriarchate, many of the more recently erected OCA parishes (and not a few of the older ones) are indeed now pan-Orthodox. St George's fits that mold, in that it's history isn't tied to any one ethnicity.
The styling 'Orthodox Catholic' was pretty common in a lot of Orthodox jurisdictions early in the 20th century. That was particularly true of, but not limited to, parishes of: the Russian Metropolia (a portion of which would evolve to become the OCA); what would eventually become the American Carpatho-Russian Diocese; and parishes of the Ukrainian Orthodox Church in the USA. All of those were heavily populated by faithful who left communion with Rome over issues that arose from conflict with Latin hierarchs particularly in the areas of trusteeship and priestly celibacy. However, the usage was not unknown among other of the Orthodox Churches as well.
St George's only dates back to 1962, about 2 decades after the last of the schisms that rocked the Eastern Catholic communities. The usage was much less common by then, but not unknown. In short, it's a genuine Orthodox temple - not a vagante
(although that kind of mized terminology usage is very common in that genre).