Sorry for this question, but have been trying to figure it out for a while...
I'm trying to install a SIOX for ImageJ using the updater, but the update option (Help > Update imageJ) don't show any option to get plugins directly from the web, only to update ImageJ. and can't find any other link to an "updater" as suggested in the main page.
So, I downloaded a jar file Siox_Segmentation-1.0.5-20160117.192327-11.jar and copied it into plugins/jars, re-open ImageJ... but it didn't work either. I'm working with MacOSX and ImageJ 1.49 installed using home brew.
Thanks for any advice.
Carlos Alberto
The ImageJ updater functionality is part of ImageJ2 (which includes full backwards compatibility to ImageJ 1.x and is also part of Fiji, as you discovered).
You can download vanilla ImageJ2 from here.
Information on how to follow an update site is available on the ImageJ wiki.
For general usage questions about ImageJ, the ImageJ forum is the best place to ask.