Looking for solutions2--  While I found nothing  to confirm Joseph Lane was ever a slave holder, I did find some extraordinarily interesting material on Lane for which I am enthusiastically grateful to you.  As I have no time at the moment to digest all this, I'll be very brief:
First, that Oregonian opinion piece with the link here does claim Lane was a slave owner and cites  several sources to back him up, such as the Oregon Encyclopedia and Wikipedia.  However, I can find NO place where they  actually state Lane was a slave owner.  

However, there is a reference to the idea that some have claimed Peter Waldo, a young black man who lived with him on his ranch was a slave.  This linked to a fantastic source, truwe/tina, on Southern Oregon History.  This has an incredibly extensive list of historic  items on the complex relationship between Lane and Waldo, much of which was new to me.
Thanks again LFS2, you've given me much to ponder.