Technically no. In practice, well, anyone who's to the left of liberalism.
Well Social Democracy is, in essence, just a more moderate form of Socialism. It involves the gradual evolution from Capitalism to a Socialist society through the democratic process.
What that means is, through steady regulation and government oversight, private business would gradually become socialist in nature.
Personally I still see Social Democracy as Socialism, but I understand if you think otherwise.
In practice we admit anyone that's 'left of liberalism' (sorry for this extremely late reply). You just need to say your opinion about the following things when applying (feel free to post them here, message me, or put them in the normal area for when applying to a guild):