I think that with some designer chops you should be able to get the two to look like they go together. For example https://www.sitepoint.com/ is WordPress and https://www.sitepoint.com/community/ is Discourse. The header navigation matches (at least to my developer eyes) and the two have links to each other. I imagine it might be difficult to get the layouts identical (eg. 2 col with no footer vs. 4 col with 2 col footer etc.) but I think achieving color palette and logo parity should be doable with CSS. There are some differences in function but IMHO a visitor would not have much of a problem knowing the two belonged together. — No embedding necessary.