1.5.0-RC-517-g38adb08 does the same.
=========================
Update: According to
https://github.com/goldendict/goldendict/issues/640 , GD is doing full-text indexing in the background. In other words it is not idling.
Excerpt from the reference file:
"The dictionary indexing for full-text search going on in background mode and started immediately after program start, name of the currently indexing dictionary is displayed in the status line. This process can take a long time and require many RAM. If RAM size is not enough to search the index dictionary the indexing process can crash. In such cases it is recommended to turn off indexing for huge dictionaries like Wikipedias or Wiktionaries. To find dictionary which can't be indexed start GoldenDict in debug mode."
So, at some point GD will finish indexing the dictionaries and will idle (it could take a long while if you have many dictionaries).