Yes. If you drag a folder named 'Pose' into Runtime->Libraries (which already contains a folder with that name), you get the warning dialog. You'll get a warning for each duplicated sub-folder as well unless you select 'yes to All.' As the dialog says, only files in 'Pose' (and duplicate named sub-folders) with the same file name will be overwritten - nothing should be deleted. I've done this many times and never had a problem. The only potential gotcha I see would be if you had say a 'gold.jpg' in 'Reflection Maps' or 'Tesxtures' and an identically named but different file in a zip. In such a case, you'd get an overwrite. Since you're trying to create a runtime to transfer, I'd just create an empty runtime folder somewhere and add empty folders for textures, libraries, etc. inside, and unzip to there, that way, you're 100% sure of not damaging anything. Once you're done, if you need any files from the real runtime, you can copy them to the created one - assuming that's not what you're doing already.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken