How hard do you think it would be to port to VB 3.8.7? Is it even possible to get this working on it?

As there is no sidebar nor CMS in 3.x there is no way to port it to 3.x. It would need to be a completely separate mod. I would not be interested in making that mod, sorry.

Does this require any server work or do you just upload the .xml file with Add/Import Product and you're done?

Just import the xml file, and then some manual steps but no file uploads.

Hi not working with 4.20 displaying the "Array" text inside the side block

I found a typo in your instructions. See the bold text below:

Also, I don't suppose you have a sidebar modification to show normal members? :)

EDIT: I found one by Lynne last night.

I installed it on 4.1.12 p2 and worked just fine. Looks great!

The side block alignment all went out of order and avatar and names overlap each other

Works great, thank you!

Make sure you have reverted all your templates to the VB 4.2.0 versions. This happens if you still have older 4.x templates being used- there is usually a message in the top of the Admin CP saying X number of templates need to be reverted.

Good eye.

Likely due to custom styles, you will probably need to play with the CSS.