gemstash VS mimemagic

Sorry to hear. I'd say, never "bundle install" in the init script. If using docker, make "bundle install" an intermediate container. If you have your own servers, try network FS sharing your deps (and see if you're ok with the "require" latencies). Alternatively, use a gem cache proxy. You can use "geminabox" with a rubygems mirror, if you can tolerate the space and long mirroring times, or use a purposed "middleman" proxy, like gemstash, or nexus if your company is multilang.

pretty clear that they copied GPL code, needed to relicense as GPL. they did a booboo https://github.com/minad/mimemagic/issues/97

His initial commit from 12 years ago referred to ‘shared-mime-info’ in this line: Blame: https://github.com/minad/mimemagic/blame/master/script/freedesktop.org.xml

Not so fast in that claim.

First of all the infringing file is https://github.com/minad/mimemagic/blob/master/script/freede.... Sure, it is in XML. But it contains a tremendous amount of free-form text, specific sets of pattern matching rules for the data types, and so on. It is a compilation of sometimes original research on the best ways to detect file types. Ruby has other mime libraries. The reason why this one was chosen is that its detection algorithms make better choices. And the reason that they make better choices is that they copied the decision rules from a GPLed project.

But even if it were a simple compilation, it still is not guaranteed that there is no copyright. See https://en.wikipedia.org/wiki/Copyright_in_compilation for an introductory article on what can and can't be copyrighted about a compilation. And one of the elements that matters is creativity in the selection of the material. A set of rules with a lot of "look for this" while leaving out various reasonable thats that don't work so well shows considerable creativity.

That said, a judge may decide otherwise. You never know until a judge decides. But I would not presume that there is no copyright interest to be had here.