Hi Gina

You're pretty much spot on in your answer.  It's more syndicated content rather than duplicate if its put across multiple domains - but syndicated content would be heavily devalued by Google as well (to the point that it would pass little to no value on the additional sites it appears - which I believe is the Google argument behind press release services like PRWeb etc.)

But you're secondary point is more poignant with me, as it is more of a courtesy to your blogger connections not to replicate the content across other domains.  Similarly, you're missing out on the chance of writing specifically for that audience, which would increase the engagement and through traffic to your site as a result.  You should definitely take advantage of that.

A slight deviation is that I'll include a short snippet of the post when sharing it on social media. It's nice to give a quick flavour and an eye catching quote to use when sharing and I'm sure the webmaster would appreciate both the social signal and potential increase in traffic.

In summary, I wouldn't go so far as to say you could be outright penalised for doing this (although definitely wouldn't rule it out), but I would say that your syndicated content will have little to no SEO value, while it potentially irk your blogging connections.

Hope this helps!