This question seems to be out of scope: How to containerize Eris service
I would vote to include Eris in this site. The underlying technology is like a private fork of Ethereum and built very close to the EVM.
Questions and answers regarding Eris will find probably on no other site with more professionals regarding these questions.
And regarding docker: if it's related with a blockchain based plattform or approach, it should be considered welcome here.
In general, I have been thinking about where to draw the line exactly for this site for quite a long time but didn't have the chance to write it down yet. Will wrap something up on meta during the next weeks.
So far the other questions about Eris have been on-topic.
I think it should be handled by the community: if enough flag a question as off-topic, then there is probably a good reason for it. If too many such questions keep getting flagged, then we discuss a more formal policy.