CompuServe's consumer dialup service started in 1979, their non-consumer services go back to the 1960's, at basically the same time as The Source. CompuServe bought The Source sometime in the late 1980's which means it was dead before dialup online services hit the mainstream in the early 1990's. This is why you likely don't see much mention of it. Another service I used back in the day which you don't see much about is the BYTE Information Exchange, BiX, which was started by BYTE magazine.