As i know, khtml support most of the IE-isms (for compatibility, try to actve "IE support" in konqueror). And for ActiveX, it must be simply supported by a khtml plugin (as crossover plugin do)
If only it were that simple. Rather ironically the thing that led to me Wine in the first place was that I needed to use features of an ActiveX control that were only available under IE. Although it would also (in theory) work in Mozilla or Konq as well, in practice they didn't support rich enough plugin interfaces for host scripting merge (where the plugin hooks into the browsers script interpreter and partially merges them together). Hence I now sometimes need to use IE under Linux.
There are lots of IEisms that I doubt Konq replicates. ActiveX controls are sometimes a lot more complex than just displaying some controls on a page, they can actually integrate with IE to quite an impressive extent.
For instance:
- DirectX filters - DHTML Behaviours - ActiveScript (needs a vbscript interpreter as well as a JS interpreter) - ActiveX data binding - .NET integration
and so on. I expect upstream khtml could get 80% of the way there, but the remaining 20% would require tight integration with Wine and some extensive code changes.