Add comments (no body text) about imcomplete MongoDB history

dosp-survey.ltx

@@ -300,6 +300,19 @@ mostly found in projects that opt for an ongoing DOSP strategy.
 % happened? Has it happened repeatedly? Is it something investors are
 % especially concerned about?
 
+% Some people say Amazon hosted a MongoDB-as-a-service product which
+% prompted MongoDB's relicensing from AGPL to SSPL in 2018. (Then in
+% 2019 Amazon announced DocumentDB, a reimplementation of portions of
+% the MongoDB API, which Amazon provides exclusively as a service
+% within AWS -- no source code.)
+% So far I haven't found any documentation of what AWS had in terms
+% of MongoDB-as-a-service prior to 2019. Most search results relate
+% to the announcement of DocumentDB in 2019, but that seems to be
+% Amazon's reaction to the SSPL relicensing. What, if anything, was
+% AWS doing before 2019 that may have prompted that relicensing?
+%
+% People also mentioned Elasticsearch and OpenSearch - I haven't
+% looked into that.
 
 \subsection{Bounty and Sponsorship Delays}\label{bounty}