He's cute!! Maybe a Polish-Silkie mix with some frizzle genes. I really don't know the color - I would just describe him as brownish. He certainly looks like a mix so the color isn't according to any breed standard.
Since he was free to you should be OK. Don't look a gift chicken in the mouth!
He's not frizzled and he's not pure silkie. His comb and wattles seem awfully red for pure silkie. I have very few "pure" bred chickens and I love my mutts. His color is mixed and at least part partridge colored.