Maybe you should sign it and copy write it, before some jerk comes along and claims HE wrote it!
I think by putting it on FR it’s dated and credited in a way. That fact probably keeps most people from claiming otherwise.
A “derivative” work I guess (maybe also “pastiche”), but it’s all Country Joe’s structure and a lot of his phrasing. No objection from me if someone wants to use it; here’s hoping they rouse up the crowd! Good delivery is quite a skill.