One can "spring" from proprietary -> open or open -> open

taxonomy.md

@@ -13,7 +13,7 @@ legislation.
 
 # Things that are DOSP
 
-* Springing licenses that automatically convert after a particular delay
+* Springing licenses that automatically convert after a particular delay (but note that these can convert from proprietary to open source, like BUSL, or from one open source license to another, like BOSL)
 
 * A promise to (explicitly or manually) relicense older versions on a predictable schedule, when this promise is made and complied with