Add material on Sentry's FSL launch and relicensing

dosp-survey.ltx

@@ -314,7 +314,8 @@ Memgraph & 2021-10-03 & rel. +4 years & Apache v2 & REF \\
 ReadySet & 2022-08-03 & rel. +4 years & Apache v2 & REF \\
 % https://github.com/readysettech/readyset/blob/main/LICENSE
 
-Sentry & 2019-11-06 & rel. +3 years & Apache v2 & REF \\
+Sentry\footnote{Sentry subsequently relicensed under its own ``Functional Source
+License"; see below for further discussion.} & 2019-11-06 & rel. +3 years & Apache v2 & REF \\
 
 SurrealDB & 2021-12-14 & rel. +4 years & Apache v2 & REF \\
 % https://github.com/surrealdb/surrealdb/blob/main/LICENSE
@@ -413,18 +414,33 @@ organization.\footnote{See
 \otsurl{https://boyter.org/2016/08/gpl-time-bomb-interesting-approach-foss-licensing/}.}
 This approach was used for Boyter's ``searchcode-server" project\footnote{See
 \otsurl{https://www.searchcode.com/}.}, but no new development has
-taken place on this codebase since 2020, so it should now be licensed
-under GPL v3.
-
-Sentry has released a draft of its ``Functional Source License" (FSL),
-which it hopes to use for its own currently BUSL-licensed software, at
-\otsurl{https://fsl.software/}.\footnote{Disclosure:
+taken place on this codebase since 2020, so the whole project is apparently
+now licensed under GPL v3.
+
+In November 2023, Sentry published its own ``Functional Source License"
+(FSL), at \otsurl{https://fsl.software/}, and relicensed its own previously
+BUSL-licensed software under it.\footnote{See Sentry's announcement and
+discussion at
+\otsurl{https://blog.sentry.io/introduction-the-functional-source-license-freedom-without-free-riding/}.
+Disclosure:
 % TODO: What is the right phrasing for the disclosure here?
 }
-The FSL prohibits, during a period of one year, uses of covered software
+The FSL prohibits, during a period of two years, uses of covered software
 to provide services that ``compete" with the original developer's commercial
-service offerings.  Following this period, the software is licensed under
-BSD or Apache terms, without the competition restriction.
+service offerings. Other uses are generally permitted. Following this two-year
+period, the software is licensed under MIT or Apache terms, without the
+competition restriction.\footnote{FSL exists in exactly two variants, one
+which converts to the MIT license after two years, and one which converts
+to the Apache 2.0 license after two years.}
+
+BUSL expressly permits certain parameters to be set by each individual
+adopter (including arbitrary free-form license text in AUGs, so long as that
+text grants additional permissions rather than removing them).  Sentry
+disapproved of the resulting proliferation of variant terms and
+differently-phrased AUGs; it stated that, from the licensee's point of
+view, each BUSL instance is actually a substantively different license.
+Accordingly, the FSL roughly follows the BUSL's approach, while freezing
+a particular set of terms.
 
 Several cloud-oriented software projects that switched away from open
 source licensing in the past few years also adopted license terms with
@@ -433,18 +449,10 @@ Conversely, several projects that adopted BUSL included AUGs that allow
 commercial uses so long as these aren't charging third parties for the
 service of hosting instances of the software, or so long as they don't
 otherwise compete with the original developer's own service offerings.
-The FSL could be seen as codifying this policy in the main license
-itself, rather than adding it as an optional additional permission.
-% TODO: This relates back to the AUG topic because so many of the database
-%       companies added AUGs saying that you can do anything you want as
-%       long as it isn't selling hosting of the software and/or doesn't
-%       commercially compete with the developer. The non-time-limited
-%       licenses do something very similar. And Sentry is also doing the
-%       same thing with FSL, but putting it in the core license rather
-%       than in a BUSL AUG.
-
-% TODO: double-check whether any of them were time-limited
+The FSL codifies a version of this policy in the main license itself,
+rather than adding it as an optional additional permission.
 
+% TODO: double-check whether any of the others were time-limited
 
 % I think it's interesting that the AGPL doesn't seem to appeal to most
 % companies that are pursuing this kind of thing. I don't know if any of