Quite possibly.

I've taken a copy of the most recent standalone installer which precedes the api-warning-nag version. It appears to be able to install over the top of the more recent version, and when my desktop API is disabled I will install it and see what happens.

The change-log of the api-warning-nag version does not mention the warning popups and just lists a higher contrast UI as an accessibility improvement. I think I can do without those kinds of updates if it means keeping the API. Fluxon mentions a forced update, hopefully that was also a featured added with the api-warning-nag update.

The standalone installer has already been signed by Skype, so it can be passed around without worries about whether it's genuine.

(I would post all the version info but am on a different computer)

I just got a forced update with no way to cancel. But I haven't gone to OldApps to see how far back to go so that A) forced updates don't happen and B) the API and apps still work reliably. Don't know which version at which those two criteria are satisfied.