No, there won’t be a standalone version of either the Dolet for Sibelius or Dolet for Finale plug-ins.
It’s not just a matter of the legal restrictions that Leo mentions. It’s that notation applications continue to compute more and more display information in the app rather than storing it in the file. For the most accurate export possible, you need to have the files open in the application.
We have several beta testers who are using this for transfers from Sibelius to Dorico. We are getting good results from the beta and hope to release Dolet 8 for Sibelius early in 2022.