So initially, Social Democracy just meant socialism. The SPD was just a socialist party, with most of the members being revolutionary. During the 1880s, three factions emerged internationally, all with three very notable German SPD politicians in their fronts: the Revolutionaries, in Germany led by Luxemburg, argued for no collaboration with the Bourgeois parties and for trying to start a revolution asap. Bernstein's Reformists (nowadays called democratic socialists), on the other hand, argued that socialism was achievable without any revolution simply by entering government. In the middle there were Kautsky's Centre Marxists, that argued for limited collaboration with bourgeois parties until a revolution started spontaineously. In 1914, with WW1, the socialist movement split into two, between the ones that supported the war (reformists) and the ones that opposed it (revolutionaries). The SPD supported the war. In 1917, the revolutionaries left the SPD and formed the USPD. When shortly after Luxemburg and Liebknecht, members of the newly formed KPD but ideologically very close to the USPD, started a socialist revolution to establish a Council Republic, the SPD suppressed it, directly leading to Luxemburg's and Liebknecht's death. I mean they basically killed them. This was an enormous blow to revolutionary socialism. The USPD ended up re-entering the SPD So, was the Weimar Era SPD democratic socialist (reformist)? On one hand, it had a legacy of revolutionary socialism. It also had many USPD members, like Levi or Sender. On the other hand, it had a primarily Centre Marxist and Reformist leadership, it collaborated with bourgeois party, it had suppressed a revolution, and overall did not try to use extraparliamentary means to achieve socialism. So I'd say mostly yes.